In a case where a drive instruction signal in a high level for placing a first triac provided to correspond to a heat generation member in a conduction state is output from a CPU, the first triac is placed in a conduction state after a second triac provided to correspond to a heat generation member is prohibited from being in a conduction state. In a case where a drive instruction signal in a low level for placing the second triac in a non-conduction state is output from the CPU, the state in which the second triac is prohibited from being in the conduction state is released after the first triac is placed in the non-conduction state.