Abstract: [Problem] To provide a check valve and a diaphragm pump employing the same which has a good response, and in which a valve chamber can be made small so as to be hardly influenced by bubbles. [Means for Solution] A check valve includes a valve chamber 11 which is defined by a top wall 8 having an introducing port 8a of a fluid, a bottom wall 9 having an exhaust port 9a of the fluid, and a side wall, and a valve body 12a which is supported in the valve chamber 11 in a cantilever manner having its base end fixed to the side wall and its distal end formed as a free end, the valve body being arranged above the introducing port 8a. The bottom wall 9 is formed with a valve seat 9b having an inclined face 9b2 which is inclined so as to be gradually separated from the top wall 8 along the valve body 12a from the base end toward the distal end thereof.