The ultrasonic stepping motor (USSM) using spatially shifted standing vibrations shows the advantages of high torque, good controllability and open-loop operation. Due to the segmentation problem of piezoelectric materials, the corresponding step size is practically limited. The purpose of this paper is to propose and implement micro-stepping control of this USSM. Different from the available half-step operation, the proposed control simultaneously varies both the combination of phase excitations and the magnitude of applied voltages in such a way that the desired step size can be attained. Digital implementation and experimental verification are given to validate the proposed micro-stepping control.