A booster includes a booster circuit and a microcomputer. The booster circuit outputs an output voltage. The output voltage is obtained by boosting a power supply voltage. The microcomputer controls the output voltage through a feedback control based on the deviation of the output voltage from a target voltage. The microcomputer determines whether the booster is in an initial state based on a start signal or a restart signal. When determining that the booster is in the initial state, the microcomputer corrects the target voltage such that the target voltage gradually increases from the power supply voltage as time elapses until a predetermined period elapses from the start of the initial state.