To provide a facility entry/exit management system having a passage monitor preventing a wrong alarm for an authorized person returned in a midway and preventing an unauthorized person accompanying an authorized person from passing, which are defects in conventional technology.

A head-count sensor is included in the constitution of the facility entry/exit management system. A recognition code obtained by reading an ID (Identification) reading transceiver 74 is compared with a previously permitted and registered recognition code for matching; the number of recognized passed persons having the matched recognition code with head counts detected by the head-count sensor. The facility entry/exit management system is configured by using the passage monitor and an output device determining that the unauthorized persons are included when the head count detected by the head count sensor is larger than the number of the recognized passed persons.