To provide an operating screw member having reliable anti-come-off effects while maintaining function.

A knob member 10 having a first engaging inner peripheral face 15 of which a head portion 5 is fitted in rotation transmissive engagement with a screw is fitted to the head portion 5 of the screw 2. The knob member 10 has an anti-come-off portion 12 extending along a leg portion 3 of the screw 2 and having elastic property at the front end to be flexible. Into the rear of the knob member 10, an anti-come-off plug 20 is fitted which has a second engaging inner peripheral face 26 for abutting on the head portion 5 of the screw 2 to be put in rotation transmissive engagement with the head portion 5, Thus, the assembled operating screw member is obtained which is easy to assemble and easier to manufacture than the one in which a resin member is formed integrally with a screw. The anti-come-off portion fitted to the mounting member is hard to crack or damage when fitted therein or subjected to tensile force. Additionally, almost no breakage occurs in assembling work at site, and occurrence of defective goods is reduced and less parts are disposed of.