A light irradiation device includes a plurality of light-emitting portions that emit light by being supplied with a current. The light-emitting portions each have a first power supply terminal, and a second power supply terminal; a plurality of light-emitting elements; and a wiring pattern. The wiring pattern has a first wiring region and a second wiring region. Two of the light-emitting portions that are disposed adjacent to each other are disposed such that the space between the respective first wiring regions or the space between the respective second wiring regions is smaller than the space between the first wiring region of one of the light-emitting portions and the second wiring region of the other of the light-emitting portions.