To safely prevent the entry of a person or a vehicle or allow the entry by controlling a solenoid selector valve, feeding or discharging pressurized air, and erecting or prostrating a cutoff body formed with a flexible and expandable material into a rod shape.

A cutoff body 8 formed with a flexible and expandable material into a rod shape or a bag shape and fitted with a union 9 at one end is fixed to a feed pipe 3 at the upper section of a stanchion 1 erected on a base 2. The feed pipe 3 and an air feed source 20 are connected by a pressure tube 12, a solenoid selector valve 11 is provided in the middle, pressurized air is invariably fed to the cutoff body 8 to linearly extend it in the lateral direction, and it is held to cut off a passage. When a switch device 13 provided near this cutoff device S is depressed or pushed by a person or a vehicle, a control means 15 switches the solenoid selector valve 11 after a delay of a prescribed time to discharge the air. When the air is discharged, the cutoff body 8 is shrunk and drooped to allow the entry of the person or vehicle. Since the cutoff body 8 is flexible and deformable, an accident caused by a collision is avoided.