An image forming apparatus has an image bearing member on which an electrostatic latent image is formed and toner deposited to form a toner image, a heater disposed at a position out of contact with the surface of the image bearing member to output radiant heat to the image bearing member, and a heat controller for controlling rotation of the image bearing member and heat output by the heater to heat the outer peripheral surface of the image bearing member moving relative to the heater. The heater includes a lamp heater having a radiation spectrum that exhibits a major part of the peak intensity in the range of infrared wavelength from 2 to 3.5 .mu.m.