Abstract: It is intended to provide an air purification filter which has a high dry tensile strength, a high wet tensile strength in association with a high water resistance and a high water repellency and exhibits a bactericidal effect due to a gas phase reaction in a gas phase. Namely, an air purification filter having a high dry tensile strength, a high wet tensile strength (a high water resistance) and a high water repellency as well as a bactericidal effect which is obtained by blending a filter fiber having a functional group with a mixture of a modification enzyme which has an ionic polarity opposite to the ionic polarity of the whole filter fiber as described above and a bactericidal effect with an ionic synthetic resin binder having the opposite ionic polarity similar to the modification enzyme.