A monitoring system can protect the privacy of a treatment recipient while monitoring the treatment recipient being treated. A transmitter transmits a beacon signal. A beacon detector detects an RSSI(2) of the beacon signal. A monitoring device includes an imaging element, an open-close body, a beacon detector, an obtainer, and an open-close body controller. The imaging element captures an image of a treatment recipient being treated by a treatment provider through an opening. The open-close body opens and closes the opening. The beacon detector detects an RSSI(1) of the beacon signal. The obtainer obtains the RSSI(2) detected by the beacon detector. The open-close body controller controls opening and closing of the open-close body based on the RSSI(1) detected by the beacon detector and the RSSI(2) obtained by the obtainer.