The object of this invention is to provide an optical disc apparatus and an optical disc reproducing method that can realize an excellent reproducing operation by suppressing noise in the optical disc apparatus using an optical attenuator. For example, an in vivo device includes: a reaction chamber to store a detecting reagent able to react with a sample collected in vivo; and optionally a labeled-substance chamber to store a labeled substance able to bind to at least a portion of a compound resulting from a reaction of the detecting reagent and the sample. The method can be applied to all rows, which can be driven asynchronously.