An offset printing apparatus includes a frame; guide rails that are provided on the frame; a plurality of guide blocks that are provided on the guide rails; a plate table that travels via one portion of the guide blocks among the plurality of guide blocks; a print target table that travels via another portion of the guide blocks among the plurality of guide blocks; and a blanket roll that is provided on the frame; wherein transfer from the plate to the blanket roll, and retransfer from the blanket roll to the print target are performed by causing the blanket roll to successively make contact from above with a plate that is held on the plate table, and a print target that is held on the print target table; a step portion for positioning that consists of a vertical surface that is formed by a machining process so that the linearity increases and a horizontal surface is provided at mounting locations of the guide rails on the upper surface portion of the frame; and one side surface and the bottom surface of the guide rails are pressed against the vertical surface and the horizontal surface of the step portion, respectively, to be fixed.