Electric stapler, post-processing device, and image forming system

An electric stapler, comprising:

• a clamp part that is configured to include a first wall portion and a second wall portion facing each other with a predetermined gap therebetween, in which the first wall portion is movable in directions of approaching and separating from the second wall portion, and that grips a paper bundle inserted between the first wall portion and the second wall portion by moving the first wall portion in the direction of approaching the second wall portion;
• a penetration part that causes a staple to penetrate the paper bundle gripped by the clamp part;
• a clinch part that bends the staple penetrating the paper bundle to bind the paper bundle;
• a gripping release detection unit that detects that the paper bundle is released from gripping after the first wall portion moves in the direction of separating from the second wall portion from a state where the paper bundle is gripped by the clamp part;
• and
• an output unit that, after it is detected that the paper bundle is released from gripping of the clamp part, outputs a gripping release signal indicating that the paper bundle is released from gripping of the clamp part to an outside.