A supercritical fluid producing apparatus according to the present disclosure includes a gas supply line, a cooler, a pump, a buffer tank, a heating device, and a supercritical fluid supply line. An inlet port into which a processing fluid from the pump flows is formed at a predetermined position on the buffer tank, and an outlet port through which the processing fluid flows out is formed at a different position from the inlet port. The buffer tank includes a buffer tank body that stores the processing fluid from the pump, and a heater that heats the processing fluid sent into the buffer tank body.