To obtain a locking system which monitors cam-feeding unlocking, door-lock breaking or the like as well as illegal unlocking by picking or thumb-turn turning, and safely prevents an aged person, etc. from going out without approval.

The locking system 1 comprises a detecting means 2 for detecting an open/close state of a doorway based on a position of a door d of the doorway of a building, a locking means 6 for locking the door d making it impossible to be opened, alarm means 11, 12, 13 emitting an alarm, a control means 5 for monitoring and controlling the operation of these devices, and a remote control means 15. When the locking means 6 is locked, the alarm is emitted to notify the locking, and monitoring of open/close of the door d starts at the same time. When opening of the door d is detected under the situation that a command for unlocking is not given, the alarm is emitted. When the door d is unlocked under the unlocking command given from the remote control means 15, the alarm means stops and the monitoring stops.