To provide the structure of a snorkel for effectively securing smooth breathing of a diver in diving and providing safety for sure use.

One end of a tube body is provided with a ventilating head, and the other end is provided with an assembling head for mounting a mouthpiece. An intake air passage and an outgoing air passage are isolated and formed inside the tube body communicating both heads with each other, a nonreturn ball valve is provided on the end part of the intake air passage of the ventilating head, and a first membrane piece is provided at the bottom edge of the assembling head. The other end of the intake air passage is communicated with the outlet of the assembling head through a second membrane piece, and also communicated with the outgoing air passage through a third membrane piece. A fourth membrane piece is fitted to one end of the outgoing air passage, and communicated with the outlet of the assembling head through a fifth membrane piece.