The present invention generally relates to a flexible substrate for a display panel and a manufacturing method thereof, and more specifically, to a flexible substrate for a display panel which is transparent and thin and has low coefficients of thermal expansion and excellent flexibility, heat resistance, and surface roughness. The flexible substrate for the display panel in accordance with the present invention comprises a film complex structure, comprising: first films where a glass cloth is impregnated inside first heat-resistant resins; intermediate materials applied to at least one side of the first films as resins having high transmittance or same as the heat-resistant resins of the first films; and second films laminated on the intermediate materials as films previously manufactured with second heat-resistant resins.