To provide an in-hotel security monitoring system capable of surely achieving security monitoring with a little labor.

A radio IC chip 12 for recording customer information is loaded on a key card 1 recording information for opening and closing a door of a hotel. A radio gate 2 for conducting information communication with the wireless IC chip 12 is placed at an important part of the hotel. A determination part 5 for determining whether a person passing through the radio gate 2 is proper to pass or not based on the result of the information communication is provided. Only a person carrying the key card 1 recording the customer information permitting to pass is determined to be proper to pass.