The IHF refused to identify the player until the result of a B-sample is known but revealed he has been suspended immediately.
The unfancied Belarus team caused a major shock at the Olympics, defeating Sweden 4-3 in the quarter-finals before losing 7-1 to eventual winners Canada.
The player is not the first Belarussian to face allegations of doping.
Short track speedskater Yulia Pavlovic was also found to have elevated levels of nandrolone in a urine test.
She escaped with a warning from the International Olympic Committee because of a broken seal on a sample bag, but her coach and the Belarus team doctor were given an Olympic ban for their part in the affair.