A first valve portion and a second valve portion are formed in a rotary valve, wherein the first and the second valve portions are arranged in an axial direction thereof. The first valve portion includes a first and a second valve windows formed in a valve member, and a first and a second valve port openings formed in a valve housing. The second valve portion includes a third valve window formed in the valve member and a third valve port opening formed in the valve housing. The valve member is rotatable in both directions of a clockwise direction and an anti-clockwise direction, so that each of the first to the third valve port openings is respectively opened or closed by the first to third valve windows. Each of the valve windows and the valve port openings of the first valve portion is formed in a rectangular shape in its developed figure in a rotational direction of the valve member.