An additive manufacturing apparatus is adapted to produce a solid object from a liquid resin and includes a vat, a lifting platform, an optical pickup head, and a planar scanning module mounted with the optical pickup head and operable to move the optical pickup head on a two-dimensional plane. The optical pickup head includes a focusing unit that has a first laser source for producing a laser beam, at least one first objective lens, and a first collimator lens disposed between the first laser source and the at least one first objective lens, such that the laser beam passes through the first collimator lens and the at least one first objective lens to strike and cure the liquid resin during movement of the lifting platform away from the vat.