The present invention provides a substance decomposing and removing agent that has the ability to effectively and sustainably decompose and remove a wide variety of substances. This substance decomposing and removing agent contains a crosslinked acrylate moisture absorbing/releasing agent and an air catalyst that comprises a metal composition containing iron, aluminum, potassium, and titanium. The proportional content of metals in the metal composition, relative to 100 ppm of iron, is 100–500 ppm of aluminum, 0.5–50 ppm of potassium, and 0.1–50 ppm of titanium. The use of the crosslinked acrylate moisture absorbing/releasing agent causes the concentration of water vapor around the air catalyst to be sustainably high, thus causing a large amount of OH radicals to be generated from the air catalyst and enabling the air catalyst to maximally exhibit said ability to decompose and remove substances. Moreover, the crosslinked acrylate moisture absorbing/releasing agent has the ability to adsorb substances. The substance decomposing and removing agent can be included in fibrous structures and various products in which a deodorizing or antibacterial ability is sought.Cette invention concerne un agent de décomposition et délimination de substances ayant la capacité de décomposer et déliminer de manière efficace et durable diverses substances. Lagent de décomposition et délimination de substances selon linvention contient un agent dabsorption/libération dhumidité de type acrylate réticulé et un catalyseur dair qui comprend une composition métallique contenant du fer, de laluminium, du potassium, et du titane. La teneur proportionnelle des métaux dans la composition métallique, pour 100 ppm de fer, est de 100 à 500 ppm daluminium, de 0,5 à 50 ppm de potassium, et de 0,1 et 50 ppm de titane. Lutilisation de lagent dabsorption/libération dhumidité de type acrylate réticulé fait que la concentration de vapeur deau autour du catalyseur dair est maintenue à un niveau durablement él