To prevent cutting of a bent portion of a gut for supporting a lens onto a half rim by preventing application thereto of excessive force.

The fixing mechanism comprises a mounting part 2 of a half rim 1 for supporting a part of the peripheral part of the lens 20, a lens 20, and a gut 6 for fixing the lens 20 onto the mounting part 2 by pressing the peripheral part of the lens toward the mounting part 2. Supporting members 8, 11 are provided on both sides of the mounting part 2 of the half rim 1 for supporting the end part of the gut 6. The supporting members 8, 11 are disposed in dent parts 7, 10 provided on both side parts of the mounting part 2 of the half rim 1.