An electronic device comprising: a casing (2, 3, 4, 5) that includes a plurality of fins including hollow fins (5a, 5b, 5c, 5d, 5e); and substrates (7C, 7D, 7E) inserted in the hollow fins the substrates including electronic circuits, wherein each of the substrates (7C, 7D, 7E) is sandwiched between inner walls of each of the hollow fins (5a, 5d, and 5e) in a contact or non-contact manner, such that each of the substrates is inserted in one hollow fin of the hollow fins, wherein the casing (2, 3, 4, 5) includes: a first surface, a second surface that faces the first surface, a third surface that is perpendicular to the second surface, a fourth surface that faces the third surface, a fifth surface that is perpendicular to the first surface and the third surface, a sixth surface that faces the fifth surface, a first member that corresponds to at least the third surface, the fifth surface, and the sixth surface and that includes the plurality of fins (5a, 5b, 5c, 5d, 5e), and a second member that corresponds to the fourth surface, and the substrates (7C, 7D, 7E) are fixed to the second member, and the electronic device further comprises an image sensor that is arranged along the first surface of the casing (2, 3, 4, 5), that is connected to the electronic circuits, and that has a light receiving surface, and wherein the substrates (7C, 7D, 7E) are perpendicular to the light receiving surface. a casing (2, 3, 4, 5) that includes a plurality of fins including hollow fins (5a, 5b, 5c, 5d, 5e); and substrates (7C, 7D, 7E) inserted in the hollow fins the substrates including electronic circuits, wherein each of the substrates (7C, 7D, 7E) is sandwiched between inner walls of each of the hollow fins (5a, 5d, and 5e) in a contact or non-contact manner, such that each of the substrates is inserted in one hollow fin of the hollow fins, wherein the casing (2, 3, 4, 5) includes: a first surface, a second surface that faces the first surface, a third surface that is perpendicular to the second surface, a fourth surface that faces the third surface, a fifth surface that is perpendicular to the first surface and the third surface, a sixth surface that faces the fifth surface, a first member that corresponds to at least the third surface, the fifth surface, and the sixth surface and that includes the plurality of fins (5a, 5b, 5c, 5d, 5e), and a second member that corresponds to the fourth surface, and the substrates (7C, 7D, 7E) are fixed to the second member, and the electronic device further comprises a first surface, a second surface that faces the first surface, a third surface that is perpendicular to the second surface, a fourth surface that faces the third surface, a fifth surface that is perpendicular to the first surface and the third surface, a sixth surface that faces the fifth surface, a first member that corresponds to at least the third surface, the fifth surface, and the sixth surface and that includes the plurality of fins (5a, 5b, 5c, 5d, 5e), and a second member that corresponds to the fourth surface, and the substrates (7C, 7D, 7E) are fixed to the second member, and the electronic device further comprises an image sensor that is arranged along the first surface of the casing (2, 3, 4, 5), that is connected to the electronic circuits, and that has a light receiving surface, and wherein the substrates (7C, 7D, 7E) are perpendicular to the light receiving surface.