An objective lens unit manufacturing apparatus for manufacturing an objective lens unit, with a numerical aperture not less than 0.7, made up by a plurality of lenses, includes a positioning mechanism (31) for positioning one lens (2) in a cylindrically-shaped lens holder (3) of a synthetic resin material, using another lens (1), already mounted and secured to the lens holder, as a reference, and for securing the one lens to the lens holder, for setting relative positions of the one and the other lenses.