A check valve includes a tubular casing, an abutment member, a valve member and a resilient member. The abutment member is flexible, is disposed in the tubular casing, and defines a central opening interconnecting first and second spaces that are defined in the tubular casing. The valve member is disposed in the tubular casing and is movable between a blocked position where the valve member blocks the central opening to isolate the first space from the second space, and an unblocked position where the valve member is spaced apart from the abutment member such that the first and second spaces communicate with each other. The resilient member is mounted to the tubular casing and biases the valve member toward the blocked position.