Disclosed is an optical information reproducing apparatus that has a light path difference between two lights easily adjusted, has a high effect on the amplification of a signal, and detects an optical information signal of an interfering type. The optical information reproducing apparatus splits a luminous flux emitted from a laser source into a first luminous flux as a signal light and a second luminous flux as a reference light not collected on an optical information recoding medium, makes the signal light optically interfere with the reference light in a state in which the signal light and the reference light are different from each other in a phase relationship to thereby produce interfering lights, and detects the interfering lights.