Abstract: A method for manufacturing an optical information medium has a step of bending at least one of a first board and a second board having a center hole, a step of applying a radiation-curing resin onto the bent board in a doughnut form while the bent board is rotated, and a step of lapping the other board on the bent board and rotating the paired boards integrally.

Abstract: A pair of tapered work rolls are arranged to confront each other and the work rolls are shifted to locate the side edges of a material to be rolled at the tapered portions of the work rolls, by adding the quantity of the movement of the taper-initiating point by wearing of the rolls to the shift quantity of the rolls, and rolling is carried out while maintaining an effective adjustment of the crown quantity (effective shift quantity). Therefore, defects such as edge drop and high spot can be effectively prevented and the crown quantity can be freely controlled, and accordingly, a desired crown quantity can be easily obtained.