Abstract: Provided is a layout design support device for supporting design of a layout of underground facilities buried in underground of a plant, the support device including: an information acquisition module configured to acquire ground layout information relating to a layout of ground facilities arranged on ground of the plant, and design condition information relating to design of the underground facilities; a generation module configured to generate, based on the ground layout information and the design condition information, positions of a plurality of water collection points into which a liquid is collected from the ground of the plant, and a first piping route along which piping that discharges, from the plant, the liquid collected into the plurality of water collection points is buried in the underground of the plant; and an output module configured to output underground layout information indicating the positions of the water collection points and the first piping route.