A nitrogen-enriched gas manufacturing method and a nitrogen-enriched gas manufacturing apparatus which minimize variations in the compressor load in order to ensure satisfactory utilization of the performance of the compressor. Specifically, a nitrogen-enriched gas manufacturing method for separating a nitrogen-enriched gas from a raw material air containing nitrogen gas using a plurality of adsorption tanks packed with an adsorbent the method including a pressurization and adsorption step, a depressurization and equalization step, a depressurization and regeneration step, and a pressurization and equalization step, wherein in the pressurization or depressurization and equalization step, the raw material air which has been compressed by the compressor is stored in a compressed raw material air tank provided on a branch line between the compressor and the adsorption tanks, and in the pressurization and adsorption step, the raw material air stored in the compressed raw material air tank is introduced into the adsorption tank and used as a portion of the gas that pressurizes the inside of the adsorption tank.