Gerrard Scanlon, 53, was arrested after Sky Sports News broadcast footage which appeared to show some of the London club's supporters abusing Senegalese striker El-Hadji Diouf.
The delivery driver admitted unleashing a foul-mouthed tirade when he was brought before magistrates on Wednesday morning and fined £425. He was told to pay further costs of £85 and a £15 victim surcharge, Scotland Yard said.
Scanlon launched his abusive rant during an npower Championship clash at The Den, on November 18. Allegations of racism later appeared online before Sky aired the incriminating footage.
Millwall Football Club said it was "appalled" by the clips while captain Danny Shittu said he was "deeply saddened" by what he saw in the documentary and the club promised to ban any individuals for life if they were found guilty.
Scanlon, from Enfield, north London, was later accused of using threatening, abusive or insulting words likely to cause harassment, alarm or distress. He was sentenced at Bromley Magistrates' Court.
Millwall have confirmed they have handed Scanlon a life-time ban from all matches at The Den.
The club issued the following statement: "Millwall Football Club understands Gerrard Scanlon, the man caught in the recent Sky Sports News documentary uttering racist abuse at a Leeds United player, appeared at Bromley Magistrates Court on Wednesday morning.
"The club had already decided to ban Scanlon for life from all matches at The Den. We are pleased that the behaviour of this individual came to notice, and that the police and the courts have now taken action against him.
"Millwall Football Club will continue to operate a zero tolerance policy to target and ban any fan guilty of displaying racist behaviour, and we look forward to developing even closer links with other agencies, including those in the media who share our determination to eradicate racism from our game."
Source: PA
Source: PA