A synchronous motor control apparatus includes a polyphase synchronous motor, a frequency adjusting circuit responsive to the closing of a power supply switch to generate a frequency control signal for commanding to linearly increase an oscillation frequency from zero up to a given high frequency, a polyphase rectangular oscillation circuit whose oscillation frequency for polyphase rectangular waves is controlled in accordance with the frequency control signal, an energization phase adjusting circuit for generating a phase control signal in accordance with a signal related to the frequency control signal from the frequency adjusting circuit, an energization phase calculating circuit for controlling the phases of the polyphase rectangular oscillation frequency of the polyphase oscillation circuit, and a drive circuit for amplifying output polyphase rectangular signals of the energization phase calculating circuit and applying the same to a field winding of the motor.