A paper feeding device for a paper cassette of an image processing apparatus. The paper cassette is mounted at a specific position or the image processing apparatus in a manner permitting the cassette to be pulled out. A preliminary feed roller feeds the paper on the paper cassette toward a feed roller which is normally energized in a paper pressing direction. When the paper cassette is mounted in the image processing apparatus, the document setting board disposed in the paper cassette is upwardly turned by a pressing mechanism. When the paper cassette is pulled out, the feed roller from the paper cassette is turned in reverse direction. A feed channel to guide the paper from the paper cassette is formed in a curved manner, and a normally turned delivery roller is provided inside the curved channel.