A lens held by a lens holding member is to be centered easily correctly. To this end, a guide pin 21 is inserted into a guide hole 22 for positioning the lens holding member 3 with respect to the main body unit of the lens barrel 2 in a plane perpendicular to the optical axis of the lens 4 and for mounting the lens holding member for movement in a direction along the optical axis. If, in this state, each of adjustment pins 26, rotationally mounted on at least three sites on the outer peripheral surface of the main body unit of the lens barrel 2, is rotated, an offset portion 29 of the adjustment pin, offset relative to the center of rotation of the adjustment pin, is rotated, as the offset portion is engaged in an engagement hole 32 of the lens holding member 3, so that the lens holding member 3 on each site is displaced in the direction along the optical axis to adjust the tilt of the lens 4 held by the lens holding member 3.