PROBLEM TO BE SOLVED: To provide a medium processing device which can smoothly shift a medium toward a conveyance reference surface, and prevent any damage during the conveyance even if the medium is weak in strength, and being miniaturized.SOLUTION: The medium processing device 1 includes a conveying passage 10 on which a medium 2 is conveyed, a conveying means for conveying the medium 2, and an evacuation passage 52 which is connected to the conveying passage 10 to evacuate at least a part of the medium 2 from the conveying passage 10. The conveyance reference surface of the medium 2 is formed on one side of the medium width direction orthogonal to the conveying direction of the medium 2 of the conveying passage 10. The conveying means includes a conveying roller 20 for conveying the medium 2, and opposing rollers 22 which are arranged opposing the conveying roller 20. The opposing rollers 22 are supported so that the conveyance reference surface and the reverse side thereof of the opposing rollers 22 are displaceable in the conveying direction. The conveying means reciprocally conveys the medium 2 therein by using the evacuation passage 52 when shifting the medium 2 to the conveyance reference surface.