A substrate processing apparatus including a holder for rotatably holding a substrate; a coating solution supply nozzle for supplying a coating solution onto a front surface of the substrate to be processed held by the holder; a treatment chamber housing the holder and the coating solution supply nozzle; a cooling device which cools the substrate before the coating solution is supplied to the substrate, to a predetermined temperature; a heating devices which heats the substrate coated with the coating solution to a predetermined temperature; and a transferer that transfers the substrate between the treatment chamber, the cooling device and the heating device, wherein the treatment chamber, the cooling device and the heating device are partitioned from ambient air, and wherein at least the treatment chamber is connected to a gas supply mechanism having a supply source of a gas having a kinematic viscosity coefficient higher than that of air.