Providing a filter device with various functions, such as remarkable improvement of the throughput of the downstream filter, ion-removing property of the upstream filter. A filter element comprises an upstream filter and a downstream filter made of the same or different material and installed into one housing or container, wherein said downstream filter is fixed to said housing, said upstream filter is fixed to said downstream filter, both filters are concentrically arranged to each other, and when the downstream filter is not contaminated, only the upstream filter can be replaced with fresh one.