Disclosed is a headphone including a headband and two ear cups connected to opposite ends of the headband. Each of the ear cups includes a shell, a front cover, and a light sensor. The shell has an open end. The front cover covers the open end of the shell. The front cover is in a basin form and has a peripheral sidewall and a bottom wall. The light sensor is located on the peripheral sidewall of the front cover. The light sensor includes a light-emitting unit and a light detection unit. When a user wears the headphone, light emitted by the light-emitting unit irradiates a flat portion of a back surface of an ear of the user.