Within an optical disk recording/reproducing apparatus, equipped with a test writing method during the recording operation, for improving accuracy on calculating the most-suitable power and recording quality, thereby recording data through irradiation of a laser beam of a predetermined power onto a optical disk, defining test writing areas on an inner periphery side and an outer periphery side and an area recordable with data between those inner periphery side and outer periphery side, or reproducing data recorded thereon from a reflection light thereupon, wherein a controller circuit 9 executes a test writing process, with selecting a test writing area on a periphery side being large in a ratio of difference, upon basis of ratios of the differences between powers on an inner periphery and an outer periphery of said disk, which are set up at present, and control data on the inner periphery and the outer periphery, which are recorded on said optical disk loaded therein, when executing the test writing process for determining the predetermined laser power of the laser beam during executing a recording process within the apparatus.