The recycling apparatus of waste sulfuric acid for collecting waste sulfuric acid generated at a source site A, transporting it by a carrier B, and recycling it for reuse at a user site C, the recycling apparatus of waste sulfuric acid including a receiving tank for receiving virgin sulfuric acid (a) and waste sulfuric acid (b) having a concentration different from that of the virgin sulfuric acid, and including (1) a mixer alone, (2) a mixer and a concentration monitor, or a mixer and a cooler in combination, or (3) a mixer, a concentration monitor, and a cooler in combination.