PURPOSE: To obtain an optical disk with which the physical transfer of information is extremely difficult without deteriorating its practicable strength.

CONSTITUTION: The surface of a transparent substrate 18 is provided with a signal layer 23 consisting of a radiation curing type resin in an annular form. A reflection layer 19 is formed on the signal layer and a protective layer 20 is formed on the reflection layer. The signal layer 23 of such optical disk is so constituted as to have the peeling strength within a range of 20/100 to 80/100 in the method for testing specified in JIS(Japanese Industrial Standards)-K5400 to the transparent substrate 18 and to satisfy the relations Os<Or<Op and Ip<Ir<Is when the outside diameter and inside diameter of the signal layer are respectively defined as Os and Is and the outside diameter and inside diameter of the reflection layer respectively as Or and Ir and the outside diameter and inside diameter of the protective layer respectively as Op and Ip. As a result, the exposure of the signal layer by physical and chemical means without damaging recording pits is no longer possible.