A flow rate control valve CV comprises: an introduction opening 10 formed open in the axial direction of a valve body housing section 13 which is formed in a hollow shape, and allowing cooling water to be introduced therein; a first housing 11 having first to third discharge openings E1-E3 which are formed to have a smaller transverse cross-section than the introduction opening 10, are in radial communication with the valve body housing section 13, and are used to discharge cooling water within the valve body housing section 13; and a valve body 3 rotatably supported within the valve body housing section 13 and having first to third openings M1-M3, the state of overlap of which with the discharge openings E1-E3 changes depending on the rotational position of the valve body 3. The transverse cross-section of the opening of the valve body housing section 13 is reduced in the axial direction thereof from the introduction opening 10 toward the third opening M3 (third discharge opening E3), and this prevents a dra
