Abstract: An intake passage device is provided for an internal combustion engine having carburetor communicated with a connecting projection of an intake port of a cylinder of the engine, wherein the diameter of the connecting projection becomes smaller toward the inside of the intake port. A connecting pipe is provided for communicating the carburetor with the intake port. An inner end of the connecting pipe is engaged in the connecting projection. There is formed a plurality of one communication passages formed in the connecting pipe for communicating an inside of the connecting pipe with a space between an inside wall of the connecting projection and an outside wall of the connecting pipe.