A cassette unit includes: a cassette case which covers a printing medium and has a feeding opening for passing the printing medium when the printing medium is fed by a feeding roller of a printing apparatus body; a cassette hopper which receives the printing medium and comes in contact with or separates from the feeding roller in a state in which the cassette hopper is mounted in the printing apparatus body; and s shutter which is switched so as to allow the printing medium to pass through the feeding opening or to prevent the printing medium from passing through the feeding opening, the cassette case, the cassette hopper, and the shutter being formed integrally. The cassette hopper is bent in a direction in which the cassette hopper approaches the feeding roller in a first joint portion jointing with the cassette case to engage with a first engagement portion.