An optical pick-up comprising a laser source (laser diode), a plurality of optical elements, beam splitter, focusing means (microlens) and detecting means (photo diode) is disclosed. The plurality of optical elements focuses a laser beam which is emitted from the laser diode onto a magneto-optic disc, and focuses a laser beam which is reflected from the magneto-optic disc onto a photo detector. The beam splitter splits the laser beam, which is emitted from the laser diode, by reflecting a part of the laser beam at a first surface and by refracting the other part of the laser beam at the first surface. The reflected part is entered into the optical elements and the refracted part is passed through the beam splitter and then emerged from a second surface. The microlens is integrally formed on the second surface of the beam splitter by the ion exchanging method. And the microlens focuses the beam which is emerged from the second surface. The photo diode detects the beam which is focused by the microlens. The beam splitter, the beam splitter, the microlens and the photo diode are mounted on a common substrate.