Proposed is a technology for controlling a synchronous motor, wherein a command value for the voltage to be applied can be set taking a delay in the response of the current into consideration. An applied-voltage electrical angle setting method related to this proposal detects the voltage applied to a synchronous motor (M) and the current thereof, calculates a peak current value (Ip) on the basis of the detected values and calculates the phase (alpha) of the voltage currently applied, and makes a target value setting unit (20) calculate a target-current phase (beta targ) on the basis of the peak current value (Ip), and then calculate a target applied-voltage phase (alpha targ) corresponding to the target-current phase. The applied-voltage electrical angle setting method also makes a voltage electrical angle command value setting unit (10) calculate a new applied-voltage electrical angle command value (theta vtarg), on the basis of a changing angle (delta theta v) that is the result of correcting the difference between the phase (alpha) of the voltage currently applied and the target applied-voltage phase (alpha targ) with a response time constant (L/R) of the synchronous motor, a rotational speed (omega) calculated on the basis of the applied voltage and the current, and the preceding applied-voltage electrical angle command value (theta vtarg).