The present invention provides: a decontaminating agent having excellent decontaminating performance of removing harmful substances derived from flying dust and microorganisms; a cellulose fiber; and a fiber structure. This decontaminating agent for removing harmful substances derived from flying dust and microorganisms comprises a metallophthalocyanine derivative represented by formula (I) which is supported on a cellulose that is cationized with a cationizing agent. In formula (I), M represents Fe, Co or Cu; R1, R2, R3 and R4 independently represent a carboxyl group or a sulfonic acid group, wherein R1, R2, R3 and R4 may be the same as or different from one another; and n1, n2, n3 and n4 independently represent an integer of 0 to 4, wherein the requirement represented by the formula is fulfilled: 1 = n1+n2+n3+n4 = 8. The cellulose preferably has a form of a fiber.
