A plurality of handpieces used to perform an operation is connected to a main operation apparatus, which generates a driving signal, through connectors formed on the main apparatus. When an operator holds a handpiece he/she wants to use, an output line over which the driving signal is transmitted is routed to the held handpiece owing to an output of a sensor that detects a change in capacitance stemming from the hold. The operator therefore need not manually set a mode in which the driving signal is applied to the handpiece he/she wants to use. Moreover, a port number assigned to a port to which the output line is routed is indicated on a display device. The operator can readily identify the usable handpiece.