Paper creasing device and printer

A paper creasing device comprising:

• a receiving member that comprises a groove extending in a fixed direction;
• a rotary blade that is movable along the groove;
• and
• a movement mechanism that is configured to move the rotary blade along the groove at a fixed height in a range between first and second edges of paper in a width direction, the paper being placed on an upper surface of the receiving member,
• wherein the receiving member is formed to have shearing forces applied to the paper sandwiched between the rotary blade and the groove in an outside range and an inside range in the width direction of the receiving member, the outside range corresponding to at least one of the first and second edges of the paper that is located on a side where the rotary blade starts contacting the paper when the rotary blade moves along the groove, and the shearing force in the outside range being smaller than the shearing force in the inside range.