An optical information recording/reproducing apparatus for stably recording, reproducing, or erasing the information by a laser beam with respect to different kinds of optical disks is represented. This apparatus includes a processor to record, reproduce, or erase the information for an optical disk, a disk sort detector to detect the sort of optical disk, and a controller to control the processing parameters of the processor in response to an output signal from the disk sort detector. The disk sort detector reads the disk sort identifying information preliminarily recorded on the optical disk by the processor to detect the sort of disk. Or, this detector irradiates light onto labels having different reflection factors or transmission factors preliminarily provided on the optical disks by the processor and detects the reflected light amounts or transmitted light amounts from the labels, thereby detecting the sort of disk. The optical disks include disks of the type only for use of reproduction, the rerecordable type, and the writable type.