To obtain a controller of a synchronous machine capable of controlling the rotational angular speed or the output torque of the synchronous machine stably with high response regardless of operating conditions.

The controller of a synchronous machine comprises an adaptive observator unit 11a for operating the estimated flux Ψr0, current deviation signal ΔIr, estimated rotational angular speed ωr0 of the synchronous machine based on a current detected by a current detecting means 2 and a voltage command from a speed control means 100a, a unit 13a for operating and outputting a feedback gain H, a unit 12a for operating a control coordinate axis rotational angular speed ωc based on the current deviation signal, the estimated flux, the feedback gain and the estimated rotational angular speed, an integrator 21 for operating the control coordinate axis phase angle θc by integrating the control coordinate axis rotational angular speed, and a speed control means 100a for controlling voltage commands vu*, vv* and vw* inputted to a voltage applying means 3 such that the estimated rotational angular speed follows a rotational angular speed command ωr*.