A substrate processing apparatus includes a spin base on which a chuck member that holds a peripheral edge of a substrate is disposed, a motor which rotates the spin base, a heater unit which is positioned between the substrate held by the chuck member and an upper surface of the spin base, a processing liquid supply unit which supplies a processing liquid toward a surface of the substrate held by the chuck member, and a microwave generating unit which generates microwaves to a lower surface of the substrate from the heater unit. The microwave generating unit may include a microwave generating member which includes a waveguide disposed in the heater unit, microwave oscillator which is disposed outside the heater unit and a coaxial cable which connects the waveguide to the microwave oscillator.