a driving device for an ultrasonic wave motor , comprises : a stator member having an electrostrictive member and a resilient member , and adapted to generate travelling vibration wave in the resilient member by excitation with the electrostrictive member ; a moving member maintained in pressure contact with the stator member and driven by the travelling vibration wave ; a reference pulse oscillator circuit for generating reference pulses of a frequency determined corresponding to a required moving speed of the member ; an encoder for generating pulses relating to the amount of movement of the moving member ; a phase difference signal generating circuit for generating a phase difference signal corresponding to the phase difference between the reference pulses from the reference pulse oscillator circuit and the output pulses of the encoder ; and an ac voltage forming circuit for forming ac voltage signals to be supplied to the electrostrictive member , based on the phase difference signal .