During a retraction where a stylus tip separates from a work piece from a state where the stylus tip and the work piece are in contact, whether there is contact between the stylus tip and the work piece is monitored. When the contact between the stylus tip and the work piece is detected during the retraction, a probe is displaced to a position where the stylus tip does not come in contact with the work piece and a recovery process is executed. When a distance between a point on a surface of the work piece at a retraction start point and a contact point between the stylus tip and the work piece is Lm, and a value defined by (Lm−d) multiplied by a coefficient k (0