To provide a heater control device for making rotation intervals of an operation knob as equal intervals, even if stroke of a connecting member for connecting the operation knob and an air conditioner side member is not at equal intervals.

This heater control device is provided with the rotated and operated operation knob 9, a rotation member 17 rotating integrally with the operation knob 9 and formed with driving gear parts 18 and 19, a gear member 23 formed with driven gear parts 25 and 26 engaged with the gear parts 18 and 19 of the rotation member 17, and a connecting member 29 for connecting the gear member 23 and an air conditioner side, and drives the air conditioner side member according to rotation of the operation knob 9. A plurality of gear parts are formed in at least one of the rotation member 17 and the gear member 23. A transmission ratio to the gear member 23 is made different by switching the gear part to be engaged according to a rotation position of the operation knob 9.