To provide an original plate for a lithographic printing plate which enables image recording by using infrared laser beam, has high print resistance and good stain resistance, and enables development process with alkali developer or on-press development.

The original plate for lithographic printing plate has on its hydrophilic support body an image recording layer including a polymerizable composition which contains a combination of polymer particles (A), a radical polymerizable compound (B), and an infrared absorbing dye (C). Characteristically, the polymer particles (A) are polymer particles linked by covalent binding of a polymerization initiator group consisting of a sulfonium salt, an iodonium salt, a diazonium salt, an azinium salt, an oxime compound, and a triazine compound, and of at least one compound selected from auxiliary agents of a specific structure.