An image forming apparatus, comprising: an image reading part configured to read an image of a manuscript placed on a manuscript placing surface; an operation unit configured to receive an input operation; and a housing configured to accommodate the image reading part and the operation unit, characterized in that the housing includes: a first frame which includes a first accommodating portion having a bottom plate (711 A) to be supported on a predetermined support surface, the first accommodating portion having an accommodating space for accommodating the image reading part, and a second accommodating portion protruding outward in a first direction from a side surface of the first accommodating portion, the second accommodating portion having an accommodating space for accommodating the operation unit; a second frame attached to a peripheral edge portion of an opening formed on a top surface of the first accommodating portion; and an engaging mechanism configured to bring the second accommodating portion and the second frame into engagement with each other, wherein the engaging mechanism includes: engaging portions (721A, 721 B and 721C) protruding downward from an end portion of the second frame existing at the side of the second accommodating portion; and engaged portions (714C, 731 B and 718) protruding upward at the side of the first accommodating portion with respect to the engaging portions (721A, 721B and 721C), the engaged portions (714C, 731B and 718) being capable of making contact with side surfaces of the engaging portions (721 A, 721 B and 721 C) existing at the side of the first accommodating portion, the engaged portions (714C, 731 B and 718) are configured, when the second frame is attached to the first frame, to be arranged to face, across a gap, the side surfaces of the engaging portions (721 A, 721 B and 721 C) existing at the side of the first accommodating portion, and if the operation unit is operated and if the second accommodating portion is bent downward about the end portion at the side of the first accommodating portion, to be moved in the first direction and make contact with the side surfaces of the engaging portions (721 A, 721 B and 721 C) existing at the side of the first accommodating portion to engage with the engaging portions (721 A, 721 B, 721 C) thereby suppressing the downward bending of the second accommodating portion. an image reading part configured to read an image of a manuscript placed on a manuscript placing surface; an operation unit configured to receive an input operation; and a housing configured to accommodate the image reading part and the operation unit, a first frame which includes a first accommodating portion having a bottom plate (711 A) to be supported on a predetermined support surface, the first accommodating portion having an accommodating space for accommodating the image reading part, and a second accommodating portion protruding outward in a first direction from a side surface of the first accommodating portion, the second accommodating portion having an accommodating space for accommodating the operation unit; a second frame attached to a peripheral edge portion of an opening formed on a top surface of the first accommodating portion; and an engaging mechanism configured to bring the second accommodating portion and the second frame into engagement with each other, engaging portions (721A, 721 B and 721C) protruding downward from an end portion of the second frame existing at the side of the second accommodating portion; and engaged portions (714C, 731 B and 718) protruding upward at the side of the first accommodating portion with respect to the engaging portions (721A, 721B and 721C), the engaged portions (714C, 731B and 718) being capable of making contact with side surfaces of the engaging portions (721 A, 721 B and 721 C) existing at the side of the first accommodating portion,