A light irradiation device, comprising: a light irradiation section including a plurality of light-emitting elements being two-dimensionally arranged along a plane perpendicular to a first direction; and a cooling section including an inlet port and an outlet port, and configured to cool down the plurality of light-emitting elements by circulating a coolant from the inlet port to the outlet port, wherein the cooling section includes, a first plate-shaped portion being thermally connected to the plurality of light-emitting elements, a second plate-shaped portion facing the first plate-shaped portion in the first direction, a plurality of first wall portions each extending between the first plate-shaped portion and the second plate-shaped portion in a second direction perpendicular to the first direction, and arranged in a third direction perpendicular to both the first direction and the second direction, a plurality of second wall portions each extending between the first plate-shaped portion and the second plate-shaped portion in the second direction, and arranged in the third direction, and a frame portion surrounding the plurality of first wall portions and the plurality of second wall portions between the first plate-shaped portion and the second plate-shaped portion, the inlet port is disposed on one side in the third direction with respect to the plurality of first wall portions and the plurality of second wall portions, the outlet port is disposed on the other side in the third direction with respect to the plurality of first wall portions and the plurality of second wall portions, each of the plurality of first wall portions and each of the plurality of second wall portions are alternately disposed in a state of being spaced apart from each other, each of the plurality of first wall portions is thermally connected to each of the first plate-shaped portion and the second plate-shaped portion, each of the plurality of second wall portions is thermally connected to each of the first plate-shaped portion and the second plate-shaped portion, the frame portion is thermally connected to each of the first plate-shaped portion and the second plate-shaped portion, each of the plurality of first wall portions includes a plurality of first passage portions through which the coolant passes, each of the plurality of second wall portions includes a plurality of second passage portions through which the coolant passes, the plurality of first passage portions are arranged in the second direction and are biased to the second plate-shaped portion side in the first direction, and the plurality of second passage portions arranged in the second direction and are biased to the first plate-shaped portion side in the first direction. a light irradiation section including a plurality of light-emitting elements being two-dimensionally arranged along a plane perpendicular to a first direction; and a cooling section including an inlet port and an outlet port, and configured to cool down the plurality of light-emitting elements by circulating a coolant from the inlet port to the outlet port, wherein the cooling section includes, a first plate-shaped portion being thermally connected to the plurality of light-emitting elements, a second plate-shaped portion facing the first plate-shaped portion in the first direction, a plurality of first wall portions each extending between the first plate-shaped portion and the second plate-shaped portion in a second direction perpendicular to the first direction, and arranged in a third direction perpendicular to both the first direction and the second direction, a plurality of second wall portions each extending between the first plate-shaped portion and the second plate-shaped portion in the second direction, and arranged in the third direction, and a frame portion surrounding the plurality of first wall portions and the plurality of second wall portions between the first plate-shaped portion and the second plate-shaped portion, the inlet port is disposed on one side in the third direction with respect to the plurality of first wall portions and the plurality of second wall portions, the outlet port is disposed on the other side in the third direction with respect to the plurality of first wall portions and the plurality of second wall portions, each of the plurality of first wall portions and each of the plurality of second wall portions are alternately disposed in a state of being spaced apart from each other, each of the plurality of first wall portions is thermally connected to each of the first plate-shaped portion and the second plate-shaped portion, each of the plurality of second wall portions is thermally connected to each of the first plate-shaped portion and the second plate-shaped portion, the frame portion is thermally connected to each of the first plate-shaped portion and the second plate-shaped portion, each of the plurality of first wall portions includes a plurality of first passage portions through which the coolant passes, each of the plurality of second wall portions includes a plurality of second passage portions through which the coolant passes, the plurality of first passage portions are arranged in the second direction and are biased to the second plate-shaped portion side in the first direction, and the plurality of second passage portions arranged in the second direction and are biased to the first plate-shaped portion side in the first direction.