An optical disk recording and reproducing apparatus includes an optical disk memory and an optical head for writing and reading out data on and from the optical disk memory by accessing onto a track of this optical disk memory and irradiating a laser beam onto a desired track. The tracks of this optical disk memory are divided into a user inaccessible area, and non-recording area, and user accessible area which are respectively provided inside and outside of the user inaccessible area. A plurality of blocks is allocated to each track in these user inaccessible area and user accessible area. Block head data representative of a block position is recorded in each block. When the optical head inadvertently enters the user inaccessible area an operation is performed to reposition the head at the user accessible area.