According to one embodiment, a sheet post-processing apparatus includes a supporting member and a plurality of paddles. The supporting member supports the trailing end portion in a conveying direction of a sheet. The plurality of paddles rotates around a rotating shaft independently from the supporting member. The plurality of paddles nip and hold the trailing end portion of the sheet in conjunction with the supporting member from both the sides in the thickness direction of the sheet. The plurality of paddles nip and hold the trailing end portions of the following sheets, which are stacked on the sheet, one by one from the thickness direction of the trailing end portion.