To provide an on-bed determination device reducing occurrences of a false detection and an erroneous determination.

An on-bed determination device 100 includes: a load sensor 11 that is disposed on a bed 2 and detects a change in the load on the bed 2; a storage section 12 that sequentially stores detection results of the load sensor 11; and an on-bed determination section 17 that, when it is determined that, based on a detection result detected at least a prescribed time earlier that is stored in the storage section 12 and a detection result of a present time, the load the prescribed time earlier decreases, determines that a person 1 is present on the bed 2.