To facilitate assembling by providing a solid part bulged to be at least partially network-like and attaching the solid part to the side part of the network by a means for making it surface from the network in an elastomer sealing joint having a form for prescribing the network.

The casing of a stop valve actuator includes a base having a hole for fitting a control spindle, a plurality of plots are formed so as to surround the hole, an attaching hole and an orifice and thereby the base has a network structure as a whole. For this base, a network-shaped sealing joint corresponding to each plot is provided and this has bars 31, 32, 33 and 34 or the like in parallel to each other. Further, a circular part 28 for defining a hole for screw passage is provided in a side part 27, bars 35, 39 and 40 having solid parts 36, 38 and 41 are provided and the solid parts 36, 39 and 41 are pressed to the orifice constituting the base.