The present invention comprises: a formation step for forming a glass plate from molten glass using a downdraw method; a cooling step for cooling the glass plate formed in the formation step while transporting the glass plate downward in the vertical direction; a detection step for detecting the position of striae occurring in the transport direction of the glass plate cooled in the cooling step and detecting the degree of variation due to the striae; and a determination step for determining the position of striae for which the degree of variation detected in the detection step is equal to or greater than a reference amount. In the cooling step, the amount of heat retained by the glass plate is controlled in a compartment surrounded by a furnace wall so that the degree of variation at the striae positions determined during the determination step is equal to or less than the reference value.