To provide a valve device superior in a water hammer preventing property and productivity.

A cover body 15 is provided on the counter valve seat side of a base body 7 with a water storage chamber communication hole 14 communicating with a water storage chamber 8, and a water hammer reducing groove 16 is formed between the cover body 15 and the base body 7 so that one part is connected with a water flow path communication hole 13 and the other part is connected with the water storage chamber communication hole 14. The water hammer reducing groove 16 consists of a narrow passage 16B communicating with the water flow path communication hole 13, and a cylindrical passage 16C connected with the narrow passage 16B and with the water storage chamber communication hole 14 for generating a swirling current. Herein, the opening area of the water flow path communication hole 13> the opening area of a communication center hole 9> the opening area of the water storage chamber communication hole 14 is established.