Abstract: A development device includes a regulation member partially defining a developer room and configured to regulate the thickness of a developer layer on a developer carrier, the regulation member including a regulation edge facing the developer carrier to control the thickness of the developer layer on the developer carrier, and an end facing an inner wall surface of the developer room; a first seal member attached to the inner wall surface of the developer room at a position facing the end of the regulation member; and a second seal member attached to the regulation member at a portion in the vicinity of the end of the regulation member and being in contact with the first seal member to seal between the first seal member and the end of the regulation member. The second seal member is lower in hardness than the first seal member.