The Championship outfit have opted to take the action after their Senegalese attacker was sent off for making a gesture towards Brighton & Hove Albion supporters on Saturday afternoon.
"I've spoken to El-Hadji Diouf and he has apologised regarding the sending off on Saturday," manager Brian McDermott told the club's official website.
"He has accepted the sending off and the club have fined him two weeks wages which is the maximum we can do.
"I've had a good conversation with Dioufy regarding the future, he is fully committed for what is to come next season."
The 32-year-old joined Leeds on a free transfer last year following a spell with Doncaster Rovers.