A heater control device includes a temperature detector that detects a temperature of a heated object heated by a heater; an alternating-current power supply for applying an alternating current voltage to the heater; a turn-on ratio decision unit that determines a turn-on ratio of the heater based on the temperature and a target temperature; a turn-on pattern decision unit that determines a partial turn-on pattern, as the turn-on pattern of the heater, which is a pattern of a turn-on ratio higher than the determined turn-on ratio in terms of a control-period, and to which a partial turn-on instead of a full turn-on is allocated on a half-wavelength basis of the alternating current voltage within the control period based on the turn-on ratio of the heater; and a turn-on controller that controls turn-on of the heater based on the determined turn-on pattern.