This invention relates to a polyimide resin and a film using the same, wherein the polyimide resin is an imidized product of polyamic acid in which a polymerization composition including a diamine-based monomer and a dianhydride-based monomer is copolymerized, at least one of the diamine-based monomer and the dianhydride-based monomer including a monomer containing at least one selected from among an oxy group, a sulfone group and a fluoro group, the diamine-based monomer including at least one selected from among 1,3-bis(4-aminophenoxy)benzene and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, and thus the polyimide resin has improved heat resistance and mechanical properties while being colorless and transparent and can thus be efficiently applied to a variety of fields, including semiconductor insulation layers, TFT-LCD insulation layers, passivation layers, liquid crystal alignment layers, optical communication materials, protective layers for solar cells, and flexible display substrates.