A heating device for heating a rotary heated member includes a heater and a temperature detector. The heater faces the rotary heated member to heat the rotary heated member. The temperature detector faces the rotary heated member via the heater to detect a temperature of the rotary heated member. The heater includes a housing provided between the temperature detector and the rotary heated member, a through-hole provided in the housing via which the temperature detector faces the rotary heated member, and a channel provided in the housing at a position downstream from the through-hole in a direction of rotation of the rotary heated member through which an air current generated in a gap between the heater and the rotary heated member moves. The channel has a hollow cross-sectional area greater than a hollow cross-sectional area of the through-hole.