Abstract: A paper sheet processing apparatus for processing a paper sheet with conveying the paper sheet having been fed, the apparatus main body including: a paper feed section; a conveyance section; and at least one kind of paper sheet processing section, wherein a paper passable region width Wb defined as a dimension of a paper passable region of the conveyance path in width directions is set to be a maximum width dimension that permits conveyance of the paper sheet without a paper jam in the paper sheet processing section in a standby state, and wherein a prevention section for, when a feed paper sheet width Wp defined as a width dimension of a paper sheet to be fed is greater than the paper passable region width Wb, preventing the to-be-fed paper sheet 100 from being conveyed intact to the paper sheet processing section is further provided.