A thyristor starter that starts a synchronous machine, the thyristor starter comprising: a converter arranged to convert AC power into DC power; a DC reactor arranged to smooth the DC power; an inverter arranged to convert the DC power provided from the converter through the DC reactor into AC power having a variable frequency, and arranged to supply the AC power to the synchronous machine; a controller arranged to control the inverter based on a phase control angle; and a voltage regulator arranged to regulate an induced voltage of the synchronous machine by supplying a field current to the synchronous machine, wherein when a rotation speed of the synchronous machine exceeds a reference rotation speed during acceleration of the synchronous machine, the voltage regulator is arranged to control the field current such that the induced voltage increases with an increase in the rotation speed of the synchronous machine, and the controller is arranged to set the phase control angle according to the rotation speed of the synchronous machine such that a DC voltage that appears at an input terminal of the inverter is constant in spite of change in the rotation speed of the synchronous machine, characterized in that the controller is further arranged to decrease a rate of increase in the phase control angle relative to the rotation speed of the synchronous machine, as compared with when the rotation speed of the synchronous machine is less than the reference rotation speed. a converter arranged to convert AC power into DC power; a DC reactor arranged to smooth the DC power; an inverter arranged to convert the DC power provided from the converter through the DC reactor into AC power having a variable frequency, and arranged to supply the AC power to the synchronous machine; a controller arranged to control the inverter based on a phase control angle; and a voltage regulator arranged to regulate an induced voltage of the synchronous machine by supplying a field current to the synchronous machine, wherein when a rotation speed of the synchronous machine exceeds a reference rotation speed during acceleration of the synchronous machine, the voltage regulator is arranged to control the field current such that the induced voltage increases with an increase in the rotation speed of the synchronous machine, and the controller is arranged to set the phase control angle according to the rotation speed of the synchronous machine such that a DC voltage that appears at an input terminal of the inverter is constant in spite of change in the rotation speed of the synchronous machine, characterized in that the controller is further arranged to decrease a rate of increase in the phase control angle relative to the rotation speed of the synchronous machine, as compared with when the rotation speed of the synchronous machine is less than the reference rotation speed. the voltage regulator is arranged to control the field current such that the induced voltage increases with an increase in the rotation speed of the synchronous machine, and the controller is arranged to set the phase control angle according to the rotation speed of the synchronous machine such that a DC voltage that appears at an input terminal of the inverter is constant in spite of change in the rotation speed of the synchronous machine, characterized in that the controller is further arranged to decrease a rate of increase in the phase control angle relative to the rotation speed of the synchronous machine, as compared with when the rotation speed of the synchronous machine is less than the reference rotation speed.