Disclosed is a helmet or a safety cap for protecting the rider's head and a method of manufacturing the same, in which the main body of the helmet has a dual-structure so as to reduce work process when an outer surface of the helmet is painted, and weight thereof. The main body of the helmet has a dual-structure in that an outer surface thereof is formed of a thermoplastic for an aesthetic enhancement and an inner surface thereof is formed of FRP or a mixture of aramide fiber, polyethylene fiber, vinylon, carbon fiber. Thus-formed dual structure of the helmet body contributes to enhancement in impact resistance and convenience in painting, decreasing an overall weight of the helmet.