In a liquid processing apparatus a spin chuck holds a wafer having a surface supplied with a liquid to be applied through a nozzle receiving the liquid through a feed path and whether the liquid passing through the feed path has fluctuation is detected by a fluctuation detection device. Thus the liquid's condition in the feed path can be determined significantly accurately. Supplying the substrate with the liquid without fluctuation allows the substrate to receive the liquid in an optimal condition. A satisfactory liquid process can thus be performed.