A sheet material processing device 3 for performing processing on a having-been-conveyed sheet material along a direction perpendicular to the conveyance direction of the sheet material, includes: a blade member 4 including an upper blade part 42 and a lower blade part 41 that extend in the perpendicular direction and then pressing both blade parts 41 and 42 to each other so as to perform predetermined processing on the sheet material located between both blade parts; a pressing mechanism 5 for pressing both blade parts to each other; and a moving mechanism 6 for moving the blade member in the perpendicular direction, wherein in the upper blade part 42, a processing blade 421 is formed at one or more sites in the perpendicular direction, and wherein in the lower blade part 41, a receiving part for the processing blade is formed over the section facing the processing blade 421.