To provide a filtration filter by which tap water or fresh water can be easily obtained while securing rigidity.

The filtration filter 21 has a first ceramic layer 12, a second ceramic layer 15 and a nanoparticle layer 14 and the nanoparticle layer 14 is held between the first ceramic layer 12 and the second ceramic layer 15. The first ceramic layer 12 and the second ceramic layer 15 are produced by sintering a lot of ceramic particles 11 consisting essentially of silica and gaps between respective ceramic particles 11 are adjusted to between 50 nm and 500 nm. The nanoparticle layer 14 is produced by melting and mutually binding a lot of nanoparticles 13 of 3 to 5 nm particle diameter by heat treatment.