They were ahead after seven minutes when Raphinha's low cross reached Vinicius Jr and he expertly lifted the ball above the charging goalkeeper and three defenders.
Five minutes later it was 2-0 with a Neymar penalty and Richarlison added a brilliant third after a spell of juggling then a razor combination with Marquinhos and Thiago Silva that had Brazil's delirious fans dancing and neutrals everywhere purring.
Lucas Paqueta volleyed in the fourth after 36 minutes and the five-times champions played the second half as an exhibition, denied more goals only by impressive Korean goalkeeper Kim Seung-gyu, as they turned their attention to Friday's quarter-final meeting with Croatia.
Korea worked tirelessly and bravely to try to limit the damage and were rewarded for their own attacking efforts when Paik Seung-ho smashed in a brilliant long-range shot beyond Alisson 13 minutes from time.