A thin film forming apparatus including: a first chamber configured to generate a mist of a dispersion liquid, and including an outlet; a second chamber configured to receive the generated mist from the first chamber and collect particles of the generated mist having a size greater than a predetermined value, and including an inlet provided on a top of the second chamber and connected to the outlet of the first chamber, and an outlet provided on the top of the second chamber and configured to transfer, as homogenized mist, particles of the generated mist having a size less than or equal to the predetermined value due to the effect of gravity on the particles of the mist; and a third chamber configured to receive the homogenized mist from the second chamber, and including an inlet connected to the outlet of the second chamber.