PROBLEM TO BE SOLVED: To provide a treatment agent for imparting a mold resistance property to fiber and fiber to which the mold resistance property is imparted and which is excellent in terms of washing durability. SOLUTION: It is found that when a treatment agent for fiber including piroctone olamine as a mold resistance component is prepared and fiber is made to soak up piroctone olamine through exhaustion treatment using the treatment agent for fiber, fiber can be obtained to which mold resistance is imparted and which is excellent in terms of washing durability. COPYRIGHT: (C)2012,JPO&INPIT