Abstract: An adjusting mechanism for a lens comprises a mount, a sphere, a pressing ring, a positioning housing, a fixing ring, a lens, and an adjusting ring. Three protruding members are provided radially and horizontally around the circumference of the sphere. The sphere is stably disposed on the mount in an opening having a spherical surface provided on the center of the mount by three tension springs each secured between the protruding members and the mount. The inside of the sphere forms cylindrical space to accommodate the lens. The lens only axially moves with respect to the sphere by turning an adjusting ring screwed onto the sphere. The positioning housing is fixed on the mount around the sphere and the fixing ring is fastened on the top of the positioning housing.