A modular oxygen generator includes a tank assembly having a plurality of tanks coupled to one another, a lower pipe assembly disposed on a lower portion of the tank assembly and provided with pipes to supply air to the tank assembly and to discharge nitrogen, and an upper pipe assembly disposed on an upper portion of the tank assembly and provided with pipes to discharge oxygen generated in the tank assembly. The tank assembly includes a plurality of beds each of which is formed of a pair of oxygen collection tanks, an air tank storing air to be supplied to the oxygen collection tanks, and an oxygen tank receiving and storing oxygen from the oxygen collection tanks. The lower pipe assembly includes a manifold having a plurality of channels, and a plurality of first valves coupled to the manifold.