A sheet laminator laminates a two-ply sheet and a sheet-shaped medium inserted in the two-ply sheet. The sheet laminator includes a sheet feeder, a multi-feeding detector, a fixing device, an ejection device, a purging portion, a passage switcher, and circuitry. The sheet feeder feeds the two-ply sheet. The multi-feeding detector detects multiple feeding of the two-ply sheet. The fixing device fixes the two-ply sheet by application of heat and pressure. The ejection device ejects the two-ply sheet that has been fixed by the fixing device. The purging portion is disposed at a position different from the ejection device. The passage switcher switches a conveyance passage of the two-ply sheet to the fixing device or to the purging portion. The circuitry conveys the two-ply sheet to the purging portion and retries sheet feeding with another two-ply sheet, in response to detection of multiple feeding of the two-ply sheet.