To provide a purifying apparatus which has an improved purifying capability, and can be easily maintained by placing a photocatalytic filter unit in a cylinder through which a fluid to be treated flows in the axial direction and by causing a part of the unit to cross the direction of flow of the fluid.

This purifying apparatus 1 has a photocatalyst filter unit 4 placed in a cylinder 3 stood and installed on a base 2. The unit 4 comprises a photocatalytic filter 13 in the form of bands twisted and attached radially and spirally around an axial member and an excitation light emitting tube 14 inserted into the inside of the axial member. Contaminated air flowing from an inlet port 5 into the cylinder 3 by driving a fan 15 is brought into contact with the photocatalytic filter 13, and various compounds in the contaminated air is oxidatively decomposed by a photocatalyst activated by ultraviolet rays from the excitation light emitting tube 14. Thus cleaned air is exhausted out of the cylinder 3. The photocatalytically functional layer homogeneously receives a large amount of ultraviolet rays, and surely carries out a photocatalytic function.