Recently, composite materials are used in various products, above all, GFRP (Glass Fiber Reinforced Plastic) is relatively inexpensive and widely used as a structure member of watercraft, or aircraft. Hat-Shaped stiffener is used as a structural member of a ship. The rising part of the GFRP Hat-Shaped stiffener, delamination occurs before the compressive stress of BWR layer of the flat part reaches the limit value. In this case, rising part is subjected to bending moment in the direction of opening the bend. The bending moment may be the cause of the delamination. In this study, we conducted the four-point bending test of GFRP curved plate and reveal the delamination strength of GFRP curved plate when subjected to bending loads.