To provide a disk rotation stabilizing plate for keeping stable recording and reproducing operation of a thin optical disk to suppress deterioration of the stabilizing plate.

The disk rotation stabilizing plate 5 is arranged opposite to an information recording and reproducing plane 1A of an optical disk 1 in the optical information recording and reproducing device and attached integrally to the optical disk 1 through a spacer 4. The plate 5 includes a stabilizing plate body 5A composed of a transparent substrate having a diameter larger than that of the optical disk 1 and protection layers 6A, 6B provided at both sides of this stabilizing plate body 5A. Each of the protection layers 6A, 6B has at least one or more layers to transmit a laser beam for recording and reproducing to/from the optical disk 1.