The disk-shaped information recording medium having an outer diameter and an inner diameter comprises a substrate having a predetermined thickness, a first side that is one side of the substrate, a second side that is the other side of the substrate, a cylindrical portion forming a through hole formed at a center of the substrate, and a thin portion formed so as to surround an outer diameter of the cylindrical portion. The thin portion is thinner than the predetermined thickness and includes a non-inclined surface and an inclined surface formed on an outer diameter side of the non-inclined surface. The inclined surface is inclined at an angle greater than or equal to 25 degrees and less than or equal to 35 degrees with respect to the non-inclined surface.