An optical encoder is configured as follows. Namely, the optical encoder includes a signal processing circuit which processes encoder signals output from a plurality of encoder heads, a control unit which specifies one of the plurality of encoder heads, sets the signal output of the specified encoder head in an on state, and further sets the outputs of the encoder heads not specified in an off state, thereby causing only the specified encoder head to output an encoder signal to the signal processing circuit, switch signal lines, and a common wiring line which is shared by the plurality of encoder heads and which transmits the encoder signals to the signal processing circuit.