A pulse wave sensor having: a light sensor unit for radiating light to a living body from a light-emitting unit and detecting reflected light or transmitted light from the living body through use of a light-receiving unit, and thereby generating an electric current signal corresponding to the intensity of received light a pulse drive unit for turning the light-emitting unit on and off at a predetermined frame frequency and duty a transimpedance amplifier for converting the electric current signal to a voltage signal and a mounting determination unit for determining a mounting status by comparing an off voltage signal obtained by the transimpedance amplifier and a predetermined first threshold voltage in a period in which the light-emitting unit is off.
