A key-less entry system including a transmitter for transmitting a door lock signal, and a vehicle onboard unit for executing a door automatic lock by detecting that a driver side door has made a transition from an open state to a closed state after reception of the lock signal. Accordingly, once the onboard unit is set to automatic lock mode by operating the transmitter, there is no need to again operate the transmitter and transmit a lock request after finishing work, but the door lock is automatically executed when the door is closed.