A method is provided for preparing an optical information medium comprising a disk-shaped supporting substrate having a center hole, an annular information recording area thereon, and an annular resin-based light-transmitting layer on the information recording area through which recording/reading laser beam is transmitted. In the formation of the light-transmitting layer, a coating fluid containing an actinic radiation-curable resin is fed onto the supporting substrate having the information-recording area formed thereon and the supporting substrate is rotated for spreading the coating fluid over the supporting substrate to thereby form a resin layer, and subsequently, the resin layer is irradiated with actinic radiation to thereby cure said resin layer while reducing the rotation speed of the supporting substrate. This method is capable of suppressing the size of the bump formed in the outer peripheral region of the light-transmitting layer.