A paper feeding device comprises a cover, a roller frame and at least one paper blocking unit. The roller frame has two side walls. The paper blocking unit is placed beside the side wall, having a projection mounted on the side wall of the roller frame and a paper blocking element including a connecting portion, the connecting portion has a positioning pillar rotatablely connected to the cover. The connecting portion extends downwards to form a stopping portion, the stopping portion further extends downwards to form a paper blocking arm, the lower portion of the paper blocking arm defines an opening communicating one side of the paper blocking arm near the side wall. The projection can stops at the stopping portion and passes through the opening of the paper blocking element to allow the document to be fed in, so the cooperation is easy, the paper feeding device works smoothly.