An image heating device includes a heater that includes a heating resistor; a rotatable tubular film in which the heater is provided in an inner space of the rotatable tubular film; a roller; and an electrification control portion configured to perform wave number control by changing the ratio of electrification ON to electrification OFF for each set control cycle. In the image heating device F1, relations tON≤τ and tOFF≤τ are satisfied, where tON represents a longest continuous electrification period in electrification patterns in which electrification is turned both on and off in the control cycle, tOFF represents a longest continuous shutoff period in the electrification patterns, and τ represents a time constant of thermal conduction with the shortest distance from the heating resistor to a contact surface of the heater that is in contact with the film.