An apparatus for reproducing information recorded on an optical recording medium, including a disk-like substrate, a spiral or concentric-shaped groove structure along tracks formed on the substrate, each of the tracks being divided into a plurality of recording units. Each of the recording units includes a dropout portion in a circumferential direction of the groove structure with the dropout portion being a non-groove portion. The groove structure is formed with a wobble in a fixed cycle in a radial direction which continues in the circumferential direction along the track. Each length of the recording units is an integer multiple of the cycle of the wobble. The apparatus includes an irradiation source for irradiating a light spot on the medium, an optical detector for detecting a reflected light from the medium, and a reproducer for reproducing information by using a signal from the optical detector.