Provided is a helmet including a half helmet-shaped helmet main body including a main body through hole at each side thereof; a shield that is rotated vertically at a front side of the helmet main body and inserted into the helmet main body and has a through hole at each end thereof so as to be detachably connected to the helmet main body; and a holder having a penetrating connection shaft at its lower surface, the penetrating connection shaft capable of being inserted through the main body through hole and the shield through hole from the outside of the helmet main body and connecting the shield to the helmet main body so as to be rotated vertically.