PURPOSE: To provide a filter assembly of a simple constitution which can be inserted into piping or similar fluid flow line, taking a less space than a conventional filter assembly.

CONSTITUTION: A filter module 11 consists of a housing divided into two compartments 15, 16 by a partition 14. At least one hollow cylindrical filter element 12 is provided in one of the compartments, and the one or a plurality of the filter elements 12 are fitted to the periphery of an opening 19 of the partition 14. A filter assembly 10 comprises a plurality of filter modules 11 mounted in a fluid flow line 13 such that incoming fluid enters one of the components, flows through the walls of the filter elements and filtered flow emerges from the other compartment.