The present invention provides a method for improving the air quality in the limited space and the equipment using thereof. The said method is that the air suctioned from the limited space is transferred to the outside of the limited space and acts as an air source for making oxygen. The oxygen is extracted from the said air source and the waste gas generated thereby is directly discharged to the outside of the limited space. The oxygen extracted is transferred into the limited space and offered the said space by means of the oxygen-supply controller. In addition, the atmosphere is supplemented into the limited space when the air inside is suctioned out. The equipment for the said method includes an indoor machine positioned in the limited space, an outdoor machine and an atmosphere supplement equipment. The present invention can supplement the atmosphere into the limited space while suctioning the air from the space, and can circulate, cool (heat), dehumidify and disinfect the air in the limited space at the same time. Consequently the quality of the said air in the limited space is improved effectively and the oxygen concentration in the limited space is ensured at a prescribed range.