<p>A plunger (45) and a piston (46) are displaceably held in a housing (104) for opening and closing a valve path (107) defined in the housing (104), and a single common seat block (44) provided for the plunger (45) and the piston (46) is fixed to the housing (104) and has seat portions (47) each formed from a soft material for respective of the plunger (45) and the piston (46) to be pressed thereon. This arrangement provides a valve device which is simplified in structure and can be manufactured with reduced man- hour.</p>
