To provide a filter apparatus having a large effective filtering surface area.

A filter apparatus has a filter tank having an inflow port of a liquid to be filtered and the annular multilayered prepack screen assembly 7 having an outflow port of a filtrate provided in the filter tank. The screen assembly 7 includes three or more cylindrical screens 9, 10, 11 having different diameters coaxially arranged in the filter tank so that the common axis thereof extends in the vertical direction of the filter tank. Annular spaces 12, 13 are formed between the cylindrical screen 9, 10, 11 and packed with two or more different filter materials achieving mutually different filtering functions.