The present invention provides a cassette loading device for an image forming apparatus including a sheet feeding portion within which a cassette for accommodating sheets is loaded, and a sheet feeding device arranged in the sheet feeding portion and adapted to feed the sheet from the cassette loaded within the sheet feeding portion. The cassette loading device has a guide for guiding the cassette to be loaded; a cassette shifting device rotatable along the guide means and having pins engageable with the cassette inserted into the sheet feeding portion; a driver for driving the cassette shifting device; vertical surfaces formed in the cassette and against which the pins are abutted to shift the cassette; and horizontal recesses formed in the cassette and adapted to direct the pins toward the vertical surfaces. The present invention further provides an image forming apparatus which includes an image forming apparatus for forming an image on the sheet being fed, and the above-mentioned cassette loading device.