A gas supplying unit of a substrate treating apparatus is proposed. The gas supplying unit includes: a gas distribution plate having a first surface and a second surface opposite the first surface, and having first gas supply holes formed through the first surface and the second surface; a shower head having a third surface being in close contact with the second surface and a fourth surface opposite the third surface, and having second gas supply holes formed through the third surface and the fourth surface to be connected to the first gas supply holes; and heat transfer members having first ends inserted in at least one of the gas distribution plate and the shower head and second ends being in contact with any one of the shower head and the gas distribution plate.