The exposure device includes: a light output device outputting light for exposing a charged image carrier, and including light-emitting elements caused to emit light or not through a control using a light-emission signal, switch elements provided corresponding to the light-emitting elements, and sequentially turned on to set the light-emitting elements ready to emit light, a transfer-signal generating unit generating a transfer signal for sequentially turning on the switch elements, a light-emission signal supply unit supplying the light-emission signal to the light-emitting elements, and a detection unit causing the transfer-signal generating unit to generate a transfer signal having cycles whose number is larger than that of the light-emitting elements, and detecting a potential of an output region of the light-emission signal supply unit while making an output from the light-emission signal supply unit high impedance; and an optical member focusing light outputted by the light output device onto the image carrier.