Rerouting apparatus for rerouting data including multimedia data. The light receiving unit includes an effective light receiving part having light receiving cells arranged in matrix form in a first direction in which a position of the light spot moves as the object moves along a direction of an optical axis of the light emitting unit, and in a second direction orthogonal to the first direction. The corner portion positioned in an inner side in a width direction of the main groove is set to an inner corner portion and the corner portion positioned in an outer side is set to an outer corner portion.