A fixating device has a first rotatable member in contact with an unfixated image borne on a recording medium, a second rotatable member forming a nip together with the second rotatable member, a first heater for heating the first rotatable member, a second heater for heating the second rotatable member, and power supply controlling means for controlling the supply of electric power to the first heater and the second heater. The power supply controlling means is adapted to control the supply of electric power so that when the electric power supplied to the first heater is Wa and the electric power supplied to the second heater is Wb and the ratio when the recording medium is nipped between and conveyed by the first rotatable member and the second rotatable member is Dp=Wa/Wb and the ratio during standby is Ds=Wa/Wb, there may be established Dp>Ds.