PURPOSE: To obtain an oxygen enriching apparatus which is widely used by providing an inverter whose power supply voltage of the apparatus can be chosen from DC 12V, DC 24V, and AC 100V.

CONSTITUTION: An electric power source is firstly set in a 12-volt battery 114 to be loaded on a car, and the engine of the car is started and idled. When a switch 111 of the power source is turned ON, DC 12V is changed to AC 100V by an inverter 113, and a vacuum pump 5 and a fan 3 are operated. The oxygen is taken out from the atmospheric air through a selective oxygen permeable membrane module 4, forced into an activated carbon filter 7 and a microbe filter 8, and supplied to the outside of the apparatus through a flowmeter 9. The atmospheric air is sucked through an air filter 2 by operating the fan 3, and supplied to the module 4. The by-product nitrogen-enriched air 6 is discharged to the outside of the apparatus while cooling the vacuum pump 5.