To perform detection as correctly as possible without forcibly imposing burden on a medical service worker when a patient physically assaults the medical service worker so as to fall onto a bed or a patient pushes the medical service worker down onto the bed.

A determining part 14 compares a load value to be put onto the bed and a comparison value obtained by adding a prescribed value to the weight of the patient using the bed. When the determining part 14 determines that the load value exceeds the comparison value, a control part 10 operates a notifying part 15 so as to notify the occurrence of an abnormal state. Thus, when the load exceeding the weight of the patient is put onto the bed, the occurrence of the abnormal state is notified by the determination that not only the load of the patient but the load of the medical service worker are put onto the bed. Consequently, the occurrence of the abnormal state on the bed is detected as correctly as possible without forcibly imposing burden on the medical service worker, so that erroneous notification is reduced.