In a cassette for accommodating therein a photo-sensitive recording medium, a pair of cassette halves formed of synthetic resin are united together to form a cassette body having defined therein an accommodating chamber for the recording medium. A drawing opening is formed in an outer surface of the cassette body. The recording medium is drawn out of the accommodating chamber through the drawing opening. An optically inert feed passage is defined by cooperation of a wall section of one of the pair of cassette halves with a wall section of the other cassette half when the one and other cassette halves are united together. The feed passage has one end thereof communicating with the accommodating chamber and the other end communicating with the drawing opening such that the recording medium passes through the feed passage when the recording medium is drawn out of the accommodating chamber through the drawing opening.