To provide a filter medium for an air filter, in which a phenomenon of leakage is suppressed, and which is manufactured in high yield and the quality of which is stabilized, and to provide a method for manufacturing the filter medium, and an air filter unit formed by using the filter medium.

This filter medium is a laminate containing at least one layer of a PTFE (polytetrafluoroethylene) porous membrane 1 and at least one layer of an air-permeable supporting material 2. Electrically conductive powder 3 is stuck to the membrane 1, preferably, to the interface between the membrane 1 and a layer adjacent to the membrane 1 and furthermore to the insides of the pores of the membrane 1. Carbon black is preferably used as the powder 3.