A filtration apparatus and a filtration method are provided. The filtration apparatus includes a filter medium, a first filter layer of a first filter aid disposed on an upstream side of the filter medium, and a second filter layer of a second filter aid disposed on an upstream side of the first filter layer. The first filter aid has a particle size distribution primarily including coarse particles, a representative particle diameter of which is smaller than a representative dimension of openings in the filter medium. The first aid forms bridges over the openings. The second filter aid has a particle size distribution primarily including fine particles, which are smaller than the first filter aid and which themselves cannot form bridges over the openings. The openings of the filter medium and the particles of the second filter layer are adjusted in size by bridging phenomenon of the first filter aid.