An object of the invention is to accommodate sheets, as coming from two image forming units, in a small-sized sheet accommodating apparatus. The individual sheets S from the first and second image forming units are fetched in different directions X1 and Y1 by a sheet pedestal and accommodated in a stack. The sheets S are registered by stoppers which can be moved in the fetching directions X1 and Y1, respectively. The sheets can be fetched in registration by inclining the sheet pedestal into first and second modes and can be fetched in an image forming direction and in a sheet direction by turning at least the sheet pedestal in a horizontal direction. The sheets S are stapled as the post-processing and are discharged in a discharge direction X2 along the fetching direction X1 from the sheet pedestal by a push member.