In an optical disk apparatus having an exclusive RF detector plane mounted therefore, as a method of obtaining a synthesized readout signal based on band-synthesis is used in order to obtain a readout signal having a good S/N ratio, a waveform distortion easily caused by a delay time difference or a sensitivity difference in the playback at higher speeds can be prevented. In order to correct the delay time difference or a sensitivity error in two channels of RF signals to be band-synthesized according to the selection of the sensitivity or playback speed, a delay time controller, a sensitivity controller, and a selector for selecting a combination method are engaged. An information holder for such control or selection is also provided.