Disclosed is a positive or negative lithographic printing plate precursor which can form an image at high sensitivity by heating or heat developed by light-heat conversion, requires no development processing after image writing, has good sensitivity and excellent printing durability, is significantly improved in scumming resistance, and can directly make a plate by operating an infrared laser based on a digital signal, the precursor comprising a polymer compound having a functional group changeable in hydrophilicity by heat, acid or radiation and an under layer with which the polymer compound combined, wherein the polymer compound is a straight-chain polymer compound directly combined at an end of a polymer chain thereof with a surface of the under layer by chemical bonding, or comprises (i) a polymer backbone chemically combined with a surface of the under layer and (ii) a straight-chain polymer compound combined at an and of a polymer chain thereof with the polymer backbone and having a functional group changeable in hydrophilicity.