Provided is an apparatus that can reduce a braking force of a medium separating mechanism to thereby reduce occurrence of paper jams only by attaching a medium supply device to an image forming apparatus body. The medium supply device is configured to be attached to an image forming apparatus body including a medium separating mechanism, and includes a medium conveying mechanism that supplies a recording medium from stacked recording media to a predetermined position, and first mechanism that reduces a braking force generated in the medium separating mechanism.