A present-on-bed determination apparatus includes: a sensor unit usable with a bottom bedding and configured to measure biological displacement of a human subject on the bottom bedding so as to output a measurement signal showing a measurement result a first signal processing unit configured to amplify the measurement signal with a first gain so as to output a first output signal a first A/D conversion unit configured to output a plurality of first level values obtained by A/D conversion of the first output signal and a determination unit configured to determine whether or not the human subject is present on the bottom bedding in accordance with a dispersion indicator that indicates dispersion degree of the plurality of the first level values.
