An image forming apparatus includes a housing including a first wall portion extending in a vertical direction, a second wall portion extending in the vertical direction on a side opposite from the first wall portion, and an internal space formed between the first wall portion and the second wall portion. In a first state in which a sheet cassette is not attached to the housing, a cover member seals an opening portion formed in the second wall portion and through which the sheet cassette passes through, and forms part of the second wall portion. In a second state in which the sheet cassette is attached to the housing, the cover member is pivoted by being abutted by part of the sheet cassette and covers a top of a portion of the sheet cassette that is exposed to the outside of the housing.