To provide a sheet processor and an image reader capable of properly processing a sheet carried from an external part.

A processing means 126A processes the sheet P carried from the external part. A control means controls driving of a sheet carrying means 117 carrying the sheet P to the processing means 126A, and can carry the sheet P in the specific timing to the processing means 126A by forming a loop in the carried sheet P by stopping the sheet carrying means 117 once before the sheet P reaches the processing means 126A.