According to an aspect, an illumination device includes: a plurality of light-emitting elements arrayed in a matrix along two directions; and a substrate on which the light-emitting elements are provided. The substrate has a plurality of partial regions. The light-emitting elements are arranged in the partial regions such that four light-emitting elements are arrayed in a two-by-two matrix along the two directions in each of the partial regions. Two light-emitting elements adjacent to each other in each of the partial regions are arranged at a first interval in one direction of the two directions. Two light-emitting elements adjacent to each other with a boundary of two partial regions adjacent to each other along the one direction interposed therebetween are arranged at a second interval in the one direction. The first interval is shorter than the second interval.