Disclosed is a flexible substrate module that uses a flexible substrate and has sufficiently excellent heat dissipation properties against a mounted heat source, and sufficiently excellent flexibility and accumulation. The flexible substrate module (1) is configured such that a printed wiring layer (12) is formed as a surface layer laminated to the surface side of a flexible insulated base material (11), and a heat source (14) is mounted on the printed wiring layer (12); and is characterized by having, as rear surface layers that are laminated on to the rear surface side of the flexible insulated base material (11), a plurality of laminated thermal expansion promotion layers (21, 23) in the flexible substrate module (1) facing and attached to a casing (K) to which the module is to be attached, made from a highly heat conductive material and for promoting expansion, towards the casing (K) to which the module is to be attached, of the surface area of hot spots that are heat-transferred from the heat source (14) to the printed wiring layer (12).