AIR BAG

PROBLEM TO BE SOLVED: To provide an air bag capable of suppressing excessive expansion of an air bag body at a gas introduction part due to gas introducing with a simple structure.SOLUTION: Main base cloth parts 21, 21 and a sub base cloth part 41 are jointed at a first joint part 42 at both sides of an introduction pipe 46 formed into a cylindrical shape by joint of the sub base cloth parts 41 at a second joint part 43. The introduction pipe 46 regulates expansion toward both side direction at a gas introduction part 29 of an air bag body 15 without using an additional expansion regulation member. With a simple structure, excessive expansion of the air bag body 15 at the gas introduction part 29 due to gas introducing can be suppressed.