An optical pickup apparatus comprising: a photo detector configured to receive light reflected from a medium; a housing mounted with the photo detector; and a projecting portion projecting from the housing, the projecting portion including a displacement preventer configured to prevent displacement of the photo detector or an adhesive relative to the housing, the displacement preventer including a fixing portion formed to extend along a plurality of directions, the photo detector being provided on the housing by applying the adhesive to the displacement preventer.