Provided is an apparatus for manufacturing a glass sheet (G), which is configured to form the glass sheet (G) by fusing streams of molten glass together at a lower edge (4) of a forming device (1) while causing the streams of molten glass (Gm) to flow downward along both outer surface portions (3) of the forming device (1) by an overflow downdraw method, the forming device (1) including protruding pieces (7), which protrude downward from the lower edge (4) of the forming device (1), and are arranged at least at both widthwise end portions of the lower edge of the forming device (1), the protruding pieces (7) each having a distal end (9) formed by a straight line substantially parallel to the lower edge (4) of the forming device (1).