A sheet stacking apparatus includes an alignment roller which conveys a sheet to a sheet positioning member and an opening and closing shutter which is disposed so as to face a sheet stack surface of a sheet stack guide. The sheet positioning member abuts a sheet end in a sheet conveying direction to align the sheet. The sheet is stacked on the sheet stack guide. The opening and closing shutter has a regulating area where sheet conveying guide and buckling of the sheet are regulated from an upstream side to a downstream side in the sheet conveying direction of the alignment roller. A guide interval formed between the opening and closing shutter and the sheet stack surface can be changed. Therefore, in sheet conveying positioning, the buckling can securely be prevented in the sheet stack guide.