The object of the present invention is to provide a gasket forming mold with a structure in which curling of the reversing section of the gasket molding does not occur easily. To achieve said object, the forming mold for integrally forming an endless shaped gasket has forming grooves as cavities in the parting surfaces of the forming mold and the forming grooves have a reversing section in a part thereof. The reversing section has two linear portions and the ends of the two linear portions are connected by an arc-shaped curved section. The two linear portions are arranged at literally-symmetrical positions and are arranged so that a distance therebetween is enlarged little by little from one end toward the other. The ends where said distance is enlarged are connected by the circular arc-shaped curved section.