A synchronous-machine starting device includes an induction voltage operating unit calculating an induction voltage induced to an armature of a synchronous machine based on an estimated phase representing a position of a rotor, an estimated rotational speed of a rotor, an AC voltage signal, and an AC current signal, and outputting an induction voltage signal representing the calculated induction voltage, a selection unit selecting and outputting one of the induction voltage signal received from the induction voltage operating unit and the AC voltage signal received from the AC voltage detection unit, and a feedback operating unit outputting a speed signal representing the calculated estimated rotational speed based on calculated phase error to the induction voltage operating unit, and outputting a position signal representing the calculated estimated phase to the electric power conversion control unit and the induction voltage operating unit.