In an optical receiver and amplifier and an optical coupler, a technique for stabilize operations at turning on/off of a power supply by a simple configuration is desired. An optical receiver and amplifier includes: a photodiode generates a photocurrent in response to a light input; an output section outputs output voltage being a low level or a high level in response to a magnitude of the photocurrent by using a power supply voltage supplied from a power supply; and an output control circuit controls an input voltage of the output section such that the output voltage is set to the low level when the power supply is turned on or off during a period where the power supply voltage is lower than a predetermined value. The output voltage can be set to the low level so that an additional circuit for preventing malfunction is not needed.