A position control device includes: a storage unit that stores a deviation, between time from transmitting an ultrasonic wave until receiving a reflected wave and a reference time, in an (n−；1)-th line when an ultrasonic probe unit scans the (n−；1)-th line of a surface of a sample before the ultrasonic probe unit moves to an n-th line； and a processing unit that determines a position of the ultrasonic probe unit when the ultrasonic probe unit scans the n-th line of the surface based on the deviation in the (n−；1)-th line, and calculates a deviation in the n-th line between time from transmitting an ultrasonic wave until receiving a reflected wave and the reference time when the ultrasonic probe unit scans the n-th line of the surface. The processing unit determines the position of the ultrasonic probe unit in a direction perpendicular to the surface to make the deviation zero.
