<p>An optical disk is provided which comprises two sheets of substrates; (1) or two sheets of substrate (1) and a reinforcing plate (4) or a reinforcing rim; or one sheet of substrate (1) and a reinforcing plate; (4) which are bonded to form an integrated body having a spacer (3) interposed there-between, said spacer (3) being made of elastomeric foam having a specific gravity of not more than 1.5 and an expansion ratio of not less than 1.5 as the material of the said spacer.(3)</p>
