To provide a locking system which carries out unlocking, based on a result of monitoring of a device state.

According to the locking system, an opening/closing monitoring IC tag 86 is bonded to a rear surface of a glass frame 111 at an upper right location thereof, and a monitoring antenna 68 is bonded to a main frame 110 at a location opposed to the tag. Then an opening/closing monitoring IC tag 186 is bonded to a wooden frame 112 at a location inside a right frame, and a monitoring antenna 168 is bonded to the main frame 110 at a location opposed to the tag. The distance between each antenna and the corresponding IC tag is set to about 3 mm when the frames are in a closed state. Then an R/W unit always polls the IC tags via the antennas. When the glass frame 111 or the main frame 110 is opened so that the distance between the antenna and the IC tag exceeds about 5 mm, communication between them is disabled, which is instantly detected. Further an antenna 128 for a key is embedded in an upper portion of a key hole 120. Therefore when the key with a built-in IC tag for the key is inserted, the R/W unit reads out an ID code, and a locking solenoid is energized only when the read ID code is a registered one, to thereby draw a plunger and unlock the device.