An electronic device includes a heat generating member arranged in a body, and a heat transmission member of a shape of a three-dimensional body having at least a first surface that is joined to the heat generating member and a second surface that is joined to an inner surface of the body. The first surface of the heat transmission member has an area greater than or equal to an area of the heat transmission member joined to the heat generating member, and an entire area of the second surface is joined to the inner surface of the body.