An apparatus and method is disclosed which can efficiently execute construction of a contents management database and setting of a reproduction list. An inner raceway surface formed on the inner race is located to be offset from a line of action common to a radial component of a contact pressure acting on a contact point between the inner race and the input disk and a radial component of a contact pressure acting on a contact point between the inner race and the output disk toward an outer race. The decoding process is performed on a sampled value obtained by sampling a signal read out from a magneto-optical disk at a predetermined sampling period. The first exposing part includes a first light transmitting portion and second light transmitting portions.