A substrate processing apparatus includes a first process chamber in which a target substrate is processed, a first tank connected to the first process chamber to supply a first chemical to the first process chamber, a second process chamber in which the target substrate is processed, and a second tank connected to the second process chamber to supply a second chemical to the second process chamber. A metal ion contained in the first chemical supplied to the first process chamber has an ion concentration greater than an ion concentration of the metal ion contained in the second chemical supplied to the second process chamber.