surface 20 is substantially flat and top surface 21 gradually approaches bottom surface 20 from the center of top surface 21 towards the both ends thus leg 10 is tapered narrowing down in a longitudinal direction semi arc shaped bearing 22 is formed at the longitudinal center of top surface 21 of leg 10 shaft 11 includes a round bar shaft section 23 and plate shaped brackets 24 arranged at both axial ends of shaft section 23 semi arc recess 25 which covers shaft section 23 of shaft 11 is formed at the center of clamp plate 12 flanges 26 are formed integrally with recess 25 on both ends thereof as clearly illustrated in fig5 a radially lower half of shaft section 23 of shaft 11 is fitted in bearing 22 of leg 10 the remaining radially upper half of shaft section 23 that is fitted in bearing 22 of leg 10 is covered with recess 25 of clamp plate 12 flanges 26 of clamp plate 12 are fixed to top surface 21 of leg 10 with screws recess 25 has a slightly smaller radius of curvature than shaft section 23 therefore the inner surface of recess 25 is pressed against the outer peripheral surface of shaft section 23 with a pressure equal to or higher than a predetermined value as a result frictional resistance f 1 is caused between the contact surfaces as illustrated in fig6 tilt angle adjusting device 1 provided with the foregoing structure is mounted in a rear portion opposite to the plane on which a projection lens is arranged of housing bottom surface 30 of projector.