There is provided a purification apparatus that packages two apparatuses that respectively perform separation treatment and purification treatment into a single apparatus, to reduce a size of the apparatus and facilitate easier transportation to the site, and to improve a treatment amount of contaminated earth and sand per unit time. The purification apparatus includes a drum rotatable around an axis, a sieve having a cylindrical shape and being fixedly accommodated in the drum, a first blade having a spiral shape and being provided between the drum and the sieve, and the second blade having a spiral shape and being provided in the sieve. In the purification apparatus, soil charged into the sieve is separated with the sieve, only the contaminated earth and sand are gathered in a treatment tank between the drum and the sieve, and a chemical agent is introduced into the treatment tank for the purification treatment.