A brass instrument includes a mouthpiece configured to convert vibrations of player's lips into sound and take the sound inside; a bell configured to magnify a volume of the sound taken by the mouthpiece and release the sound to the outside; and a main tube intervening between the mouthpiece and the bell, and is characterized in that the main tube includes a main tube body formed to spread out in a spiral manner in a state in which side surfaces of the main tube body are closely attached to each other, and a part of the closely attached side surfaces of one of the tubes constitutes a part of the side surface of the closely attached other tube.