<P>PROBLEM TO BE SOLVED: To provide a negative-working photosensitive material which achieves improvement of the developability of a non-image area and enhancement of adhesion to a substrate and satisfies both of soiling resistance in printing and printing durability, and a negative-working planographic printing plate precursor using the negative-working photosensitive material. <P>SOLUTION: The negative-working photosensitive material is obtained by sequentially layering on a support an undercoat layer and a photosensitive layer including a polymerization initiator, a polymerizable compound, and a binder polymer, wherein the undercoat layer includes a polymer including a structural unit (a) including at least one carboxylic acid and/or carboxylic acid salt and a structural unit (b) including at least one carboxylic acid ester, and the content of the structural unit (a) including at least one carboxylic acid and/or carboxylic acid salt in the polymer is 30-90 mol.%. The negative-working planographic printing plate precursor is obtained using the negative-working photosensitive material. <P>COPYRIGHT: (C)2009,JPO&INPIT 
NEGATIVE-WORKING PHOTOSENSITIVE MATERIAL AND NEGATIVE-WORKING PLANOGRAPHIC PRINTING PLATE PRECURSOR