To provide a sheet processing device and a sheet conveying method which suppress a sheet end from drooping downward by means of corrugating of a sheet.

The sheet processing device 7 includes: a detecting section 60 detecting the sheet fed by a sheet feeder 24; a standby tray 10 stacking the fed sheet thereon and including a first roller 66 conveying the sheet; a second roller 65 facing the first roller and turning to come into contact with and separate from the first roller; a protrusion connected to a bearing of a rotary shaft of the second roller, and contacting with and curving the sheet when the first roller contacts with the second roller; a processing tray 12 stacking the sheet dropped and supplied from the standby tray, and retaining the sheet while the sheet is subjected to a requested processing; and a controller separating the second roller from the first roller at a prescribed timing following a detection result by a detecting section while the sheet is conveyed to the standby tray.