To provide a coating supply system which is capable of applying a large amount of a coating liquid with a constant temperature at a breath.

A pump 8 of a second circulation pathway 3 is always driven to keep the temperature of a development solution in a tank 1 constant. In this state, a pump 4 of a first circulation pathway 2 is driven to send the development solution pumped out by the pump 4 to a slit nozzle 6. At this time, if an on-off valve 7 is closed, the development solution supplied into the slit nozzle 6 flows down from a slit like discharge port 6d to the lower part in a state like a curtain and is supplied to the surface of a substrate to be treated.