To provide a valve device which conducts valve opening operation without abnormally increasing the pressure in a valve casing and requiring large operation force.

A marking for indicating a rotating position of a handle 12 when a valve element 4 is changed from a fully closing state to a specified opening state (semi-fully closing). By matching the marking, the valve element 4 is operated from a position in the fully closing state to a position in the specified opening state (semi-fully closing) without a burden. Valve opening operation can be conducted without abnormally increasing the pressure in the valve casing 8 and requiring large operation force, and the fully closing state of the valve is ensured.