<p>A seat block capable of simply and reliably maintaining intimate contact property of a seal section without being affected by use conditions. A seat section forming body (43) is provided in a housing (67), having a valve path (66) formed in it, such that a piston (28) for opening and closing the valve path (66) can be seated on the seat section forming body (43). A spring member (23) applies elastic force to the seat section forming body (43) to hold it in cooperation with the housing (67).</p>
