A sheet aligning apparatus, comprising: a sheet storing section having an open end portion through which a sheet is conveyed in and out; a conveying-in section (R3, R10) having a conveying-in path to convey a sheet into the open end portion of the sheet storing section; a conveying-out section (R4, R11) having a nip section between a conveying-out drive roller and a conveying-out follower roller in a conveying-out path, to convey out a sheet stored in said sheet storing section from the said open end portion, wherein the conveying-in path and the conveying-out path form a meeting point at the open end portion; a stop member arranged in the sheet storing section so as to oppose the open end portion; a shifting section (125, M3) to shift up the stop member from an initial position to a first position, wherein when the stop member is positioned at the initial position, the stop member comes in contact with the leading end of a preceding sheet conveyed into the sheet storing section through the open end portion, and when the shifting section shifts the stop member from the initial position to the first position, the said preceding sheet is shifted inversely, i.e. in the conveying-out direction, by the stop member while the back end of the said preceding sheet proceeds as the leading end in the conveying-out direction, i.e. as the inversed leading end, from the meeting point to the conveying-out path so that a succeeding sheet is allowed to be conveyed from the conveying-in path into the open end portion; and a shift regulating section to regulate the said shift of the said preceding sheet when the shifting section shifts the stop member from the initial position to the first position, so that the said back end of the preceding sheet is prevented from proceeding more than a predetermined distance due to the inertia of said preceding sheet provided by said shift, characterized in that said shift regulating section includes a shift regulating member to come in contact with the said back end of the preceding sheet on the conveying-out path when the shifting section shifts the stop member from the initial position to the first position, so that the said back end of the preceding sheet does not reach said nip section. a sheet storing section having an open end portion through which a sheet is conveyed in and out; a conveying-in section (R3, R10) having a conveying-in path to convey a sheet into the open end portion of the sheet storing section; a conveying-out section (R4, R11) having a nip section between a conveying-out drive roller and a conveying-out follower roller in a conveying-out path, to convey out a sheet stored in said sheet storing section from the said open end portion, wherein the conveying-in path and the conveying-out path form a meeting point at the open end portion; a stop member arranged in the sheet storing section so as to oppose the open end portion; a shifting section (125, M3) to shift up the stop member from an initial position to a first position, wherein when the stop member is positioned at the initial position, the stop member comes in contact with the leading end of a preceding sheet conveyed into the sheet storing section through the open end portion, and when the shifting section shifts the stop member from the initial position to the first position, the said preceding sheet is shifted inversely, i.e. in the conveying-out direction, by the stop member while the back end of the said preceding sheet proceeds as the leading end in the conveying-out direction, i.e. as the inversed leading end, from the meeting point to the conveying-out path so that a succeeding sheet is allowed to be conveyed from the conveying-in path into the open end portion; and a shift regulating section to regulate the said shift of the said preceding sheet when the shifting section shifts the stop member from the initial position to the first position, so that the said back end of the preceding sheet is prevented from proceeding more than a predetermined distance due to the inertia of said preceding sheet provided by said shift, characterized in that said shift regulating section includes a shift regulating member to come in contact with the said back end of the preceding sheet on the conveying-out path when the shifting section shifts the stop member from the initial position to the first position, so that the said back end of the preceding sheet does not reach said nip section.