In order to efficiently transport a filtration target liquid to a separation membrane module and to facilitate additional simplification of equipment in a filtration device including the separation membrane modules in which a plurality of lines thereof are disposed in series, a filtration device according to the present invention is a filtration device including a plurality of separation membrane modules each of which separates a liquid to be filtrated into a permeated liquid and a non-permeated liquid, in which the filtration device includes: a series non-permeated liquid flow channel that forms a series unit by connecting non-permeation sides of the plurality of separation membrane modules in series; and a parallel permeated liquid flow channel that forms a parallel unit by connecting permeation sides of the plurality of separation membrane modules in parallel.