A cooling device includes a mounting surface, a cooling fin on a rear surface side of the mounting surface, and a cooling passage for cooling the cooling fin with a liquid refrigerant. The refrigerant flows from a flow inlet to the cooling passage and discharges from a discharge outlet. The cooling passage comprises a first surface provided with the cooling fin, a second surface opposing the first surface, and a wall portion between the first surface and the second surface, and is longer than a channel connecting the flow inlet and the discharge outlet. The wall portion has a first wall portion extending from the second surface to the first surface, and a second wall portion extending in parallel with the first wall portion from the first surface to a height exceeding a top portion of the first wall.