To effectively remove a chemical substance generated in a room such as a clean room or the like.

This chemical filter unit 30 arranged in a room is constituted by incorporating a fan for circulating indoor air and a chemical filter for removing the chemical substance in circulating air in a casing having a suction port and a blowoff port. The suction port is provided in one end of the casing having a cylindrical shape while the blowoff port is provided in the other end thereof and the chemical filter is arranged inside the suction port or blowoff port so as to be made detachable, from this port. The chemical filter unit 30 is arranged in the clean room 21 and the chemical substance in circulating air is removed by the chemical filter unit 30 while circulating at least a part of indoor air.