PURPOSE: To provide the title agent which is excellent in workability and safety, can remove efficiently a film-forming staining substance such as tar, chewing gum or varnish, and can generally cope with recent environmental pollution.

CONSTITUTION: The title agent comprises a water-soluble surfactant of an HLB of 7 or above used to make the agent water-soluble, a pyrrolidone solvent and optionally a terpene, can remove without fail a film-forming staining substance and excels in solubility, odorlessness, prevention of resticking, safety and easiness of aftertreatment. As compared with a conventional dissolving agent, this agent is noninflammable, nontoxic, difficultly decomposable and highly safe, can remove a film-forming staining substance speedily without fail, and can ensure comfortable aftercare.