To provide a monitor device for an entry monitoring system capable of adapting information about the locked or unlocked state of an electric lock to a variety of embodiments of the subject of monitoring.

The monitor device 4 controls the electric lock 14 to be locked or unlocked upon the input of authentic identification information. The monitor device 4 includes an electric lock control means 53 for monitoring the locked/ unlocked state of the electric lock 14 and sending control commands to the lock 14, and a lock mode management means 62 for setting lock modes and controlling or managing the change of the lock modes, the lock modes including two modes: a monitor mode in which unlocking of the electric lock 14 is regarded as an abnormality; and a release mode in which unlocking of the electric lock 14 is not regarded as an abnormality. When it determines a user to be the authentic user according to the identification information, the lock mode management means 62 sets the lock mode into the release mode; and the mode is returned to its original mode or standby after a predetermined time has elapsed, in the constitution of the monitor device 4.