Surface temperature control device for maintaining a constant temperature by control of current supply

An image forming apparatus, comprising:

• image forming means for forming a toner image on a recording material;
• fixing means for fixing the toner image on the recording material, said fixing means having a conveying member for conveying the recording material and a heater for heating said conveying member;
• control means for controlling a start and a duration of a second current supply for said heating source, said control means calculating the duration for the second current supply in accordance with a time required for a first current supply for said heating source and a time required for a surface temperature of said member to be heated from a minimum value to a maximum value during application of the first current supply, said control means starting the second current supply after the surface temperature of said member which has been heated by the first current supply has fallen to the predetermined temperature.