The invention discloses a side mark positioning device. The side mark positioning device comprises a wallboard, a pull mark roller, a gauge plate and a parallel roller; two ends of the parallel rollerare connected to the wallboard; the pull mark roller is arranged on the parallel roller, and the two are contacted with each other and can relatively roll; the pull mark roller is rotationally assembled on the gauge plate; and the bottom edge of the gauge plate is contacted with the parallel roller. The side mark positioning device is further provided with a pull mark roller adjusting mechanism;the pull mark roller adjusting mechanism comprises a connecting part with one end relatively rotationally connected to the pull mark roller, a pressure adjusting structure connected to the connectingpart and capable of providing upward or downward acting force to the connecting part, and a roller angle adjusting structure connected to the other end of the connecting part and capable of moving tothe rolling direction of a tension roller; and the pressure adjusting structure is fixedly connected to a pressure applying mechanism. The side mark positioning device can unify and adjust the pressure of the side mark positioning roller to papers, and is high in adjusting precision, simple in structure and low in cost.