PURPOSE: To enable painting in a small installation space, in a painting method using a paint containing a prepolymer having a free isocyanate group, by simultaneously spraying a chemical agent for accelerating the curing of the paint to a substrate.

CONSTITUTION: A paint is one containing a prepolymer having a free isocyanate group and cured by the contact with ammonia or amine. The paint and ammonia or amine are together applied to a substrate 3 by a spray coating mechanism 4 but the paint 3 is supplied from a paint pressure feed tank 22 through a compressed air supply source 21 and sprayed by a painting gun 4a while, simultaneously with the spraying of the paint, ammonia or amine 23 is supplied from a separate pressure feed tank 25 through a compressed air supply source 24 to be sprayed by a painting gun 4b. Therefore, the formation and curing of a paint film can be performed without providing a special operating region such as a curing chamber.