A photoelectric sensor capable of preventing a malfunction caused by mutual interference is provided. The photoelectric sensor (1) includes: a light projecting unit (100) that repetitively emits a setof pulse light, which follows a projected light pattern in which a light projecting period is made different by a fixed time, as signal light; a light receiving element (202) that receives the signallight; and a light receiving controller (206) that distinguishes a light incident state and a light blocked state based on a received light signal from the light receiving element. The light projecting unit (100) has a first pattern having the light projecting period increased by a fixed time and a second pattern having the light projecting period reduced by a fixed time as the projected light pattern, and in the first and second patterns, a pulse indicating a shortest period is included in the light projecting period other than the shortest period.