A seat sensor is arranged for each of a plurality of seats. A pulse-signal supplying unit supplies a pulse signal with a different timing to the seat sensor. An operator identifying unit detects, when a first operator sit on any one of the seats operates an operating unit, the pulse signal supplied to the seat sensor by the pulse-signal supplying unit through the first operator and the operating unit, and identifies the first operator based on a timing of a detected pulse signal. An operation control unit performs a control depending on an operation performed on the operating unit by a detected first operator.