To provide a fan filter unit, capable of reducing noise generated from an axial fan in spite of a compact structure.

A partition plate is provided within a body case having a surface plate and a back plate so as to separate the surface plate from the back plate, and the axial fan is disposed on the partition plate, whereby a passage extending from a suction port provided on the back surface side to an outlet port provided on the surface plate side is formed in a bypass manner. A filter is disposed within the passage in such a manner that it is located in a position where the main surface or reverse surface of the fan is invisible as viewed from one side of the outlet port at an angle of 90-0° to the plane of the outlet port and as viewed from one side of the suction port at an angle of 90-0° to the plane of the suction port.