To provide a multiple optical-axis photoelectric sensor capable of preventing detecting operation from being performed in a state that the optical axis pitch of a light projector does not coincide with that of a light receiver in the multiple optical-axis photoelectric sensor provided with the projector or the light receiver which are respectively constituted by connecting a plurality of light projection units or a plurality of light receiving units in series.

Respective light projection units 13a to 13c of the light projector 10 and respective light receiving units 23a to 23c of the light receiver 20 are respectively provided with pitch display lamps 15a to 15c, 25a to 25c formed as notification means. On the pitch display lamps 15a to 15c, 25a to 25c, the sorts of optical axis pitches of light projection elements 14a to 14c of the light projection units 13a to 13c or light receiving elements 24a to 24c of the light receiving units 23a to 23c are displayed.