A biological sensor capable of improving the signal-to-noise ratio of a detection signal obtained by a light-receiving element and amplified by an amplifier is provided.The biological sensor includes a driving signal generating unit that generates a pulse-form driving signal, a light-emitting element that emits light in response to the generated driving signal, a light-receiving element that outputs a detection signal based on an intensity of received light, an amplifying unit including first and second operational amplifiers that amplify the outputted detection signal, an offset signal generating unit and a voltage dividing resistor group that generate a pulse-form offset voltage for offsetting a reference potential of the first operational amplifier when amplifying the detection signal and apply the offset voltage to the first operational amplifier, and a computation unit that obtains biological information by processing the detection signal amplified by the amplifying unit.
