An electronic cash register includes department keys for instructing a department registration operation. A department memory includes a memory area for storing an automatic complex registration number which defines an automatic complex registration operation when a corresponding department key is actuated. A complex registration memory stores a set of desired PLU code numbers related to the automatic complex registration number. Thus, when a desired department key is actuated, the registration related to a plurality of commodities defined by the set of PLU code numbers stored in the complex registration memory is automatically conducted.