The aim of the invention is to stably manufacture a flexible copper clad laminate comprising a copper foil of superior flexibility and a polyimide resin layer. In a method for manufacturing a copper clad laminate comprising the copper foil and the polyimide resin layer by applying a polyimide precursor resin solution to the surface of the copper foil and then drying and hardening in a following heat treatment process, by maintaining 3-40 minutes in the temperature range of 300-450 DEG C in the heat treatment process by using an electrolytic copper foil as the copper foil, wherein the average crystal grain diameter of the copper foil grows up 2-8 times of that before the heat treatment process.