PROBLEM TO BE SOLVED: To have an extremely simple structure of sensor electrodes, to arrange a large number of sensor electrodes, and to use an alternating electric field of commercial power as a signal source, and to have a transmitter of a specific frequency for capacitance measurement. Provide a bed leaving detection system. SOLUTION: The bed leaving detection system is laid under a bed cloth 3 which is a dielectric material whose thickness is changed by being compressed by the weight of a human body P and exerts an elastic force, and is discretely discretely arranged on an insulating film. A sensor sheet 2 in which a large number of sensor electrodes 4 are discretely provided, and an alternating electric potential of a commercial power CM is induced in a large number of sensor electrodes 4 via the floor cloth 3 by a potential charged in the human body P on the floor cloth 3. It has a monitoring device that detects the amplitude of the electrostatic induction current that changes with the cycle of the alternating electric potential, and obtains the distance D between the human body P and a large number of sensor electrodes 4 from the amplitude. [Selection diagram] Fig. 1【課題】センサ電極の構造が極めて簡単で多数のセンサ電極を配置可能で、かつ、商用電力の交番電界を信号源として利用して、容量測定の為の特定周波数の発信器を持つ必要がない離床検出システムを提供する。【解決手段】離床検出システムは、人体Ｐの体重により圧縮され厚みが変化する誘電体材料であって弾性力を発揮する敷布３の下に敷かれ、絶縁膜の上に行列状に離散的に多数のセンサ電極４を離散的に設けられたセンサシート２と、商用電力ＣＭの交番電界が敷布３上の人体Ｐに帯電された電位によって、敷布３を介して多数の各センサ電極４に誘起され、交番電界の周期で変化する静電誘導電流の振幅を検出し、振幅から人体Ｐと多数の各センサ電極４との距離Ｄを求める監視装置とを有する。【選択図】図１
