Fixing unit and image forming apparatus equipped with the fixing unit

A fixing unit for use in passing a recording medium carrying a unfixed image through between a pair of rotating bodies which are rotated with being pressed to each other to heat and press the recording medium thereby filing the unfixed image to the recording medium, comprising:

• a first heater for generating heat energy with electric current supplied from a power source to heat up one of the rotating bodies;
• a second heater for generating heat energy with the electric current supplied from the power source to heat up the one of the rotating bodies or other components;
• and
• a switching means for changing over a first state that the first heater and the second heater are serially connected to and supplied with the electric current from the power source and a second state that the first heater is connected to and supplied with the electric current from the power source while the second heater is substantially disconnected from the power source,
• wherein the relation:
• Q11/Q21>1/8 is satisfied, where Q11 denotes a heating value of the first heater in the first state per unit of time and Q21 denotes a heating value of the first heater in the second state per unit of time.