The paper discharge mechanism comprises: a first side passage plate and a second side passage plate between which an S-shaped paper conveying passage is formed, wherein the second side passage plate comprises a paper jam detection plate and a paper pullout detection plate both pivotally connected on a frame; a first elastic element biasing the paper jam detection plate and a second elastic element biasing the paper pullout detection plate; and a first sensor and a second sensor. A surface of the paper jam detection plate facing paper is concave and is held against the paper and rotates in the direction away from the first side passage plate during paper jam; a surface of the paper pullout detection plate facing the paper is convex and is held against the paper and rotates in the direction away from the first side passage plate during paper pullout.