The purification device (1) forms minute air bubbles (12) that contain organic substances in pooled water (11), which is pooled in a water tank (10), using a gas bubble generator (20) and collapses the gas bubbles by irradiating ultrasonic waves on the pooled water using an oscillator (50) to generate hydroxyl radicals around the gas bubbles. The organic substances inside the gas bubbles are decomposed by the hydroxyl radicals generated around the gas bubbles. By decomposing the organic substances inside the gas bubbles using the hydroxyl radicals generated in the pooled water, the purification device improves the ability to purify the gas that is being purified.
