Abstract: This invention relates to a clamp type screw loosening prevention mechanism for eyeglasses parts which enables tight clamping of the end portion of the threaded rod of male screw toward the axis utilizing ingenious configulation of the female screw, which can effectively prevent loosening of all screwed parts such as temple hinge, rim closing block, pad, top rim, etc. The screw loosening prevention mechanism of the present invention consists of providing split cone projection on the exit side of the metal eyeglasses parts to be screw joined or fixed through whose piercing hole the end of the threaded rod of the male screw can come out, and by providing to the inside wall of the piercing hole which goes into this split cone projection the female screw thread which gradually reduces in inside diameter as the exit end approaches, the end part of the male screw threaded rod screwed therein is tightly clamped toward the center of axis by the spring-back resiliency of the split cone projection.