To improve safety for tunnel users by surely preventing the diffusion of smoke when a fire occurs inside a tunnel passage.

A duct 12 is arranged on the outer peripheral part of a tunnel passage 11, an air blower 13 and a smoke extinguishing device 14 are arranged on an upper duct 12a, and a large number of two-fluid nozzles 15 composed of air jetting nozzles 15a for forming an air current B in the direction of a tunnel cross section and water spouting nozzles 15b for forming a water mist stream D are provided on one side duct 12b. A suction hole 16 capable of sucking air and water mist is provided on another side duct 12c.