An electric power supply part supplies electric power to a heat-generating member and a power requiring part. A control part controls electric power supplied to the heat-generating member and the power requiring part. A first mode is to supply electric power to the heat-generating member from only a main electric power supply device and to the power requiring part from both the main electric power supply device and an auxiliary electric power requiring part. A second mode is to supply electric power to the heat-generating member and the power requiring part from only the main electric power supply device and causing electric power supplied to the heat-generating member to be smaller than a rated electric power of the heat-generating member. The electric power supplied to the heat-generating member in the first mode is caused to be larger than the electric power supplied to the heat-generating member in the second mode.