A light irradiation device for emitting light of two or more components by laser light, which a laser light source emits, to an outside, includes a diffusion optical path change member configured to convert a first color component of the laser light into diffusion light and change an optical path of the first color component; a phosphor configured to generate fluorescence of a second color component different from the first color component based on the laser light, and change an optical path of the second color component; and an optical path switch member configured to switch between a first optical path for emitting the first color component to the outside and a second optical path for emitting the second color component to the outside. Light going straight at a light diffusion position of the diffusion optical path change member is not emitted to the outside.