The invention discloses a marking machine capable of printing marks on two surfaces of size plates. The marking machine comprises a frame; the frame is provided with a feed groove, a first marking station groove, a second marking station groove and a discharge groove in sequence; a stop part is arranged on one end, near the first marking station groove, of the feed groove; the other end of the feed groove is connected with one end of a feed rail; the other end of the feed rail is connected with a discharge end of a vibration disc; a transfer mechanism is additionally arranged on the frame, and is used for enabling the size plates positioned on the feed groove to be fed into the first marking station groove, the second marking station groove and the discharge groove in sequence and to be overturned by 180 degrees in the process of feeding from the first marking station groove into the second marking station groove; and the size plates are printed with ink by a first marking machine head in the first marking station groove, and are printed with ink by a second marking machine head in the second marking station groove.