To provide a bag with a compact valve.

This bag 1 has a containing part 1a to contain a contained matter 2 inside. The containing part 1a is formed of an air containing part 1b to be inflated by sealing in air. Blowing air in/out the air containing part 1b is carried out by the valve device 3 which is equipped with a the valve main body 30 with a valve seat 30a, the valve body 31 detachably attached to the valve seat 30a, an elastic member 32 equipped in the valve main body 30 to energize to press the valve body 31 against the valve seat 30a, and a stopper part 33 attached to the valve main body 30 to stop the elastic member 32. in a middle part of the passage. The valve body 31 equipped in the passage is faced outward.