A photoelectric switch emits pulsed detection light and outputs a light detection signal as reflected light is received. For generating an on-off judgment output for switching on and off, the level of the light detection signal is shifted towards a specified level during a specified light receiving period by an amount corresponding to the difference between the specified and the level of the light detection signal at a time immediately before the pulsed detection light is expected to arrive. On the basis of thus level-shifted signal, it is determined whether at least one of the conditions for generating the on-off judgment output is satisfied. The on-off judgment output is generated at least on the condition that the levels of the light detection signal at specified timings are in a specified size relationship. According to another embodiment, pulsed detection light is emitted at least three times per cycle of noise from a fluorescent lamp and comparisons are made between a specified level and the level of the light detection signal whenever a peak of the pulsed detection light is expected to arrive, and the on-off judgment output is generated according to the majority of the results of comparisons made during a period of light emission.