JPH047019B

PURPOSE:To grasp whether or not grooves of recording tracks are formed to specific depth at a stage wherein an optical disk substrate is coated with a recording medium by forming specific pit arrays along the outer periphery, etc., of a track area for signal recording. CONSTITUTION:The optical disk substrate 5 has guide grooves as tracking guides, i.e. track area 6 for signal recording and a signal area 7 where projection and recessed pitch arrays formed at a constant frequency. The signal area 7 of the projection and recessed pit arrays formed on said substrate 5 except in the track area 6 for signal recording is a means for monitoring whether the grooves in the signal recording area 6 are formed suitably or not. The defect generation rate of the optical disk substrate 5 after the recording medium is formed is grasped quantitatively to control and secure the quality of the substrate 5.