A fluidic device unit structure in which a plurality of fluidic devices are integrated and which is effective in reducing a footprint is provided. With a fluidic device unit structure in which a plurality of fluidic devices that are connected by channels are integrated in a base member 10 in parallel, the base member 10, which has a plurality of mounting surfaces 11 on which pure-water opening and closing valves 5 are mounted, includes a pure-water circulation supply line 2 that passes through the base member 10 and that is connected in parallel to the pure-water opening and closing valves 5 via pure-water branch channels 4.