A filter medium (20) includes a first porous PTFE (11) membrane, a first air-permeable support member (12), a second porous PTFE membrane (13), and a second air-permeable support member (14). A surface of the filter medium (20) is formed by the first porous PTFE membrane (11). A bond strength (A 1 ), as measured by a 180° peel test, between the first porous PTFE membrane (11) and the first air-permeable support member (12) is higher than 1.2 N/25 mm. The first air-permeable support member (12) is an embossed non-woven fabric having one or more recessed portions and one or more projecting portions. A ratio of the area of the recessed portion or the total area of the recessed portions to the area of the embossed non-woven fabric serving as the first air-permeable support member (12) is more than 15%.
