PURPOSE: To prevent the temperature of the surface of a heat roller from dropping suddenly right after a heat roller and a pressure roller begin to rotate.

CONSTITUTION: When the roller rotating speeds and fixation temperature of an image fixation device are controlled, three modes of rotating speed are provided i.e., a 1st rotating speed Va as a fixation speed, a 2nd rotating speed Vs1 in a stand-by state, and a 3rd rotating speed Vs2 which is slower than the 1st rotating speed Va and faster than the 2nd rotating speed Vs1; when the heat roller temperature when the power source is turned on is lower than the 1st temperature Tsh which is previously set, the roller is rotated at the rotating speed Va until the heat roller reaches 2nd temperature Tin as process initialization start temperature and when there is no print start command after the 2nd temperature Tin is reached and the warmup is finished the roller is rotated at the 3rd rotating speed Vs2 for a predetermined time t1 and then at the 2nd rotating speed Vs1 thereafter.