A surface inspection apparatus is constructed of an illumination unit for irradiating a wafer with illumination radiation for inspection, and a radiation receiving unit having a CCD imaging device for detecting an image of the wafer by converging regularly reflected radiation from the wafer. The speed controller includes a monitoring module that is designed to detect, by reference to the locating data, a situation in which objects not detected by the locating system are within close range and, in this situation, issue a takeover prompt to the driver. The decision of the communication period is performed in accordance with a predetermined wake-up period, a time-out value that maintains the connection state even when no communication is taking place, and a frame length that is a unit of the communication.