There is provided a lithographic printing plate precursor that enables image recording using a laser and that provides an excellent scumming resistance and an excellent developability while maintaining a satisfactory printing durability. Also provided are a platemaking method, and a novel polymerizable monomer. A lithographic printing plate precursor has a support, and an image recording layer disposed thereon and containing a radical polymerization initiator and a polymerizable monomer that has a sulfonamide group and at least two ethylenically unsaturated groups; a lithographic printing plate platemaking method uses this lithographic printing plate precursor; and a polymerizable monomer has a sulfonamide group and at least two ethylenically unsaturated groups.