A housing of a liquid level detection device includes an inner case, which has a first wall portion, and a terminal, which has a projection that extends through the first wall portion and projects to an outside of the inner case. The first wall portion and the projection are covered with a covering portion. A first seal film, which connects between an outer peripheral surface of the projection and the first wall portion, is formed in an inside of the covering portion. A film thickness of the first seal film along an edge line of the terminal progressively increases toward the first wall portion.