A cooling water control valve device includes a housing and a valve. The housing includes an inside space, an attachment surface, at least one inlet port, and at least one outlet port. The attachment surface is in contact with an outer wall of the engine. The valve is disposed in the inside space to control communication between the at least one inlet port and the at least one outlet port by rotating. The housing includes a housing body that defines the inside space therein and a bypass passage forming member that defines at least a portion of a bypass passage. The bypass passage bypasses the valve and fluidly connects the at least one inlet port and the inside space. The housing is attached to the engine such that the attachment surface comes into contact with the outer wall of the engine.