The present invention aims to provide a fluid handling device which can be manufactured more conveniently, can easily open and close a channel, and can be miniaturized. The fluid handling device of the present invention includes: a first channel; a second channel; and a valve disposed between the first channel and the second channel, in which the valve includes: a groove-shaped valve seat disposed in a board, and a flat plate-shaped flexible layer covering the groove-shaped valve seat, and the valve communicates between the first channel and the second channel when the flat plate-shaped flexible layer and a bottom of the groove-shaped valve seat are spaced apart from each other, and blocks communication between the first channel and the second channel when the flat plate-shaped flexible layer and an inner wall of the groove-shaped valve seat are in contact with each other.