To provide a method for forming a peak of a cap, enabling the peak of the cap always to have a prescribed curvature for user's convenience and be maintained in a bent state, and further to provide a device therefor.

This method comprises heating a peak of a cap having a main body part and the peak for about 5-150 sec by steam at about 100°C in a curved state having a prescribed curvature, and cooling the heated cap for about 10-150 sec by cold wind at about 5-25°C. The device has a heating part capable of jetting the steam and a cooling part capable of jetting the cold wind, the first and second main body parts 14 having an opened upper part, a flowing-in hole 14' at one side and knob parts at the centers of the front and back faces, a storage body 20 having an opened upper part, a porous net form at each face, and supplementary knobs 22 in the upper parts of the front and back faces, and a molding member 30 curved to the prescribed curvature, having flange parts 36 at both sides, and having a space adjusting member 34 for forming a space part by a first mold 31 and a second mold 32 both having the porous net form by a connecting means 33, and fixed between the molds 31 and 32.