To provide a filter apparatus capable of preventing the back flow of a liquid and capable of providing a separate function on the central part of a filter.

The filter apparatus 1 is constituted so that an element 13 is concentrically provided in a case 11 so as to provide a predetermined interval with respect to the case 11 and a check valve 30 is provided to the gap S between the inner periphery of the case 11 and the outer periphery of the element 13 on the oil inflow side thereof. Accordingly, the back flow of the oil in a fluid circuit can be prevented after an engine is stopped. As a result, it is unnecessary to newly fill the filter and piping with the oil, for example, at the time of restarting of the engine, a problem, such that the supply of oil to respective parts is delayed, is eliminated and the reliability of the engine is enhanced.