The present invention provides a cable fixing structure in which, when a tensile force in the longitudinal direction acts on a flat cable, the stress acting on the joint between the substrate and theflat cable can be reduced by the cable fixing structure. This can prevent the electrical connection between the flat cable and the substrate from being cut off. A cable fixing structure(10) of a fuelcell stack(12) fixes together a connector housing(48) containing a substrate(50) and a flat cable(34) joined to the substrate(50). The cable fixing structure(10) includes a fixing part(78) provided for the connector housing(48), and having a convexly curved surface(100), and a heat contraction tube(80) configured to surround the flat cable(34) and the fixing part(78), and press the flat cable(34)against the convexly curved surface(100).