To provide a gas treatment apparatus which has improved treatment efficiency of a component to be treated of gas, and enables a vessel to be made compact.

A swirl flow 48 of gas G is formed by introducing the gas G from a gas introducing portion 42 into a vessel 41 and leading the flow into a swirl flow forming portion 50. By the force of the gas G when forming the swirl flow 48, liquid L injected from four liquid injection portions 53 and stored in a sump portion 60 is involved in the swirl flow 48, and the gas G is brought into contact with the liquid L, to treat the component to be treated (ammonia) of the gas G. Furthermore, even if the component to be treated (ammonia) of the gas G cannot be sufficiently treated at the swirl flow forming portion 50, during the flow of the gas G from an opening of the swirl flow forming portion 50 to the downstream side above the vessel 41, the component to be treated (ammonia) of the gas G can be efficiently treated by bringing the gas G into contact with the liquid L injected from the liquid injection portions 53.