Abstract: A manual control valve apparatus having a structure which is provided with, as a conversion mechanism, a diaphragm compressor which is held between a valve casing and a guide member, arcuate engaging grooves formed in a surface of the diaphragm presser opposite to the valve stem, and rolling elements which engage in a freely rolling manner in the engaging grooves and are supported by the lead end part of the valve stem. The bottom surfaces of the engaging grooves are made cam surfaces for causing reciprocating motion in the axial direction of the valve stem. An indicator possessing opening indicating portions indicating the rotational position of the valve stem is attached to the opposite end of the guide member from the valve casing, and furthermore, windows exposing the opening support portions are provided in an area from the circumferential wall of the handle to the end wall thereof.