Abstract: In a photomask formed with a device pattern made of a light-shielding film pattern in a transfer area on a front surface of an optically transparent substrate, the photomask includes a non-device pattern such as a product identification pattern composed of a light-shielding film pattern in a non-transfer area at a peripheral portion, wherein there is provided, at a back surface of the optically transparent substrate opposed to at least a position where the non-device pattern is formed, a light-transmission reducing thin film as light-transmission reducing means for reducing transmission of exposure light entering from the peripheral portion of the back surface of the optically transparent substrate.