To open only doors on a transmitter side among multiple doors without requiring the monitoring of doors on the opposite side by receiving the signal of a portable transmitter with directional antennas to release a door lock.

A trunk room 18 is provided under the seats of a tour bus 13, and electric locks 24, 25 are provided on flap doors 22, 23. Directional antennas 26, 27 having receiving areas 33, 34 are connected to the receiver 19 of a control device 20 controlling the locks 24, 25. When a code transmitted in the receiving area 33 by a transmitter 21 carried by a driver is received, the lock 24 of the corresponding door 22 is unlocked, and the lock 25 of the door 23 on the opposite side is kept in the locked state. Only the door 22 on the transmitter 21 side is unlocked, and the monitoring of the door 23 on the opposite side is not required. If the receiving areas 33, 34 of the antennas 22, 23 are further subdivided, the flap doors 22, 23 can be individually locked or unlocked.