To solve the following problem; it is difficult to attach/detach a lens, and it is impossible to replace lenses without special tool and skill.

By burying permanent magnets 10, 10a ..., 12, 12a..., in the long and narrow plate-like front frame 4 with temples 7 and 7a connected to the both ends and the upper part of the lens 3, the lens 3 is magnetically joined to the front frame 4. Further, by protrusively arranging a stopper 8 at the upper end of the back surface of the front frame 4, the lens 3 is easily positioned at attaching the lens 3, and by protrusively arranging a sub stopper 9 on the rear side of the leading end of the stopper 8, the lens 3 is surely fixed.