To reduce a manufacturing cost by simplifying structure and a manufacturing process.

A rotary cutter device 10 includes: a casing 12 provided with first and second wall surfaces 13 and 14; a rotor 20 rotatably supported by the casing and provided with a first flat blade 21; and a holding body 30 supported by the casing and provided with a second flat blade 31 cutting a paper P in cooperation with the first flat blade 21. The rotor 20 has a flat blade attachment part 24 provided on the casing so as to be rotatable around a separated shaft center O and disposed in a position separated from the shaft center on a plane crossing the shaft center O so that the rotational locus of one side end part forms a diameter larger than that of the rotational locus of the other end part upon rotation and a flat blade supporting part 25 supporting the first flat blade to the flat blade attachment part so that the other side end part of the first flat blade is protruded more than the one side end part in the peripheral direction of the rotational locus. The holding body 30 is provided with a holding part 32 capable of holding the second flat blade so as to be nearly parallel to the shaft center O via a prescribed interval.