To provide an installation structure for a fan filter unit wherein transmission of vibration produced on a fan filter unit is dumped to prevent an apparatus installed in a clean room from being badly affected by the vibration.

In a structure where a fan filter unit 20 is installed on a system ceiling frame 10, the fan filter unit 20 is mounted on the system ceiling frame 10 through a resilient member 30. Vibration produced on the fan filter unit 20 is absorbed in the resilient member 30 owing to vibrationproof effect of the resilient member 30 without badly affecting an apparatus installed in the clean room 1. Further, the resilient member 30 is constructed as a frame mold, and an air flow passage communicating from the inside of the framer to the outside of the frame is formed, so that air staying in the clean room and dust produced from the resilient member 30 can be discharged from the flow passage to the outside of the chamber.