A thyristor starter accelerates a synchronous machine from a stop state to a predetermined rotation speed by sequentially performing a first mode of performing commutation of an inverter by intermittently setting DC output current of a converter to zero and a second mode of performing commutation of the inverter by induced voltage of the synchronous machine. In the thyristor starter, during a first time period from start of performance of the second mode to arrival of the induced voltage of the synchronous machine at a first voltage value, a phase control angle of the inverter is changed such that a value thereof becomes larger as a rotation speed of the synchronous machine becomes higher.