The camera on a 30mph limit junction of Newport Road  is catching an average of 71 speeding drivers every day.
A survey last year found a camera on the M60 in Greater Manchester caught about 26 speeding drivers per day.
The GoSafe partnership, which runs the Cardiff camera, said 99.5% of drivers at the site met the speed limit.
It said: "Motorists should comply with the relevant speed limit, which is there for a reason."
The body also insisted that placing cameras at a location was always "a last resort".
"The revenue from speeding fines is returned back to the government and not the partnership," said Chris Hume from GoSafe.
"There is a simple message - cameras are in place to save lives not to make money."
The camera was installed in 2012, but only went into fully commissioned operation earlier this year.
It has now notched up a staggering 13,624 penalty notices for speeding - and a further 146 drivers were caught for red-light offences.

Andrew Armstrong, 33, of Mossdale Road, Manchester, pleaded guilty to one count of rape at an earlier hearing.
The victim reported the rape to police in 2002 but the Crown Prosecution Service (CPS) decided no action should be taken.
A fresh investigation was launched in 2013 when the victim reported it again. Police said the woman had "suffered for years" and been ostracised by family.
The victim and a police officer handling the case were also threatened with rape via a text message on 12 May this year when Armstrong entered his guilty plea, police said.
The threat came from an unknown number and also contained a sexually-explicit photo.
A 59-year-old man has been arrested and bailed in connection with the incident.
Det Con Rachel Wood said: "This is one of the most harrowing cases I have ever dealt with during my years as a police officer."
She said the woman had "suffered for years" knowing she had been a victim of rape and was "further tormented" because she was "ostracised from her family who refused to believe her".
"Both the victim and myself were subjected to vile sexual threats so it is even more testament to the courage and bravery of this woman that she did not back down in the face of such disgusting threats and, as a result, Armstrong has been convicted of his appalling crime." the detective said.
"She has told me that the abuse she suffered at the hands of Armstrong ruined her life, to the point where she is paranoid the same thing will happen to her own children."
Armstrong was told he would remain on the sex offenders register for life.
Det Con Wood said she hoped the sentence at Manchester Crown Court would mean the victim could now "finally start to rebuild her life".

Verheydt, who had been with Maastricht since 2015, has signed a three-year contract with Harry Kewell's side.
The 25-year-old scored 13 goals in 43 appearances in all competitions last season.
Meanwhile, Watford winger Dennon Lewis, 20, has joined the Reds on a loan deal until 31 December.
Lewis, who made 29 National League appearances on loan at Woking last season, played under Kewell when the Australian was coach of Watford's under-23 team.
Find all the latest football transfers on our dedicated page.
A speed camera in Cardiff is the busiest in Britain - catching almost three times as many drivers each day as one on a busy Manchester motorway.
[NEXT_CONCEPT]
A man who raped a 14-year-old girl in 2001 has been jailed for six years.
[NEXT_CONCEPT]
League Two side Crawley Town have signed striker Thomas Verheydt from Dutch second-tier side MVV Maastricht for an undisclosed fee.