Disclosed is a substrate drying apparatus of substrate processing apparatus including a chamber that provides a space for processing a substrate, and a fluid supply unit that supplies a process fluid to the chamber, wherein the liquid supply unit includes a supply tank in which the fluid is stored, a supply line that connects the supply tank and the chamber, a branch line branched from a first point of the supply line and connected to a second point of the supply line, and a temperature control unit that adjusts the temperature of the fluid such that the temperatures of the fluids flowing through the supply line and the branch line between the first point and the second point are different.