Punching unit and sheet post-processing device

A punching unit, comprising:

• a punching blade that forms a hole in a sheet;
• a holder that holds the punching blade;
• a biasing member that biases the holder in a retracting direction in which the punching blade moves away from the sheet;
• an eccentric cam that contacts the holder, and that rotates against a biasing force of the biasing member to move the holder in a punching direction in which the punching blade approaches the sheet;
• and
• a punching guide that extends in a moving direction of the punching blade in which the punching blade moves with respect to the sheet, and that guides movement of the punching blade,
• wherein
• the eccentric cam, when moving the holder in the punching direction, passes by a side of the punching guide in a manner overlapping with the punching guide as seen from a rotation axis direction of the eccentric cam,
• the punching quide has an elongated hole that extends linearly in the moving direction of the punching blade,
• as the elongated hole, two elongated holes are formed one at each of two positions facing each other in the rotation axis direction with the punching blade therebetween, the punching unit includes a connection pin that connects the punching blade and the holder, and
• the connection pin is inserted in a connection hole formed in an upper part of the punching blade, the connection pin projects from the punching blade to be inserted in the elongated hole on one side and an other side of the connection hole with respect to the rotation axis direction, and the connection pin is supported by the holder at end parts thereof on the one side and the other side.