Provided is a ferritic stainless steel foil for a solar cell substrate excellent in terms of threading performance with which it is possible to maintain sufficient hardness to suppress, for example, buckling during threading when a solar cell is manufactured using a roll-to-roll method. The ferritic stainless steel foil for a solar cell substrate has a chemical composition containing, by mass %, Cr: 14% or more and 18% or less, a Vickers hardness of Hv250 or more, and a Vickers hardness of Hv250 or more after the substrate has undergone an optical absorber layer growth process in which the substrate is held in a temperature range of 450° C. or higher and 600° C. or lower for a duration of 1 minute or more.