To provide an applying method for a sealing material for buildings including application of a primer, capable of ensuring waterproof performance for a long term by allowing a person to easily check if the primer is applied or not even after an elapse of years.

The applying method for a sealing material for buildings including application of a primer uses a primer containing, as an essential constituent, a chemical agent emitting light when being irradiated with ultraviolet rays. In particular, a chemical agent insoluble in a solvent and having a particle size of 0.001 mm or smaller is selected, and addition of the agent in an amount of 0.001-0.5 wt.% of the primer is desirable. Judgment on whether the primer is actually applied or not can be easily made by casting ultraviolet rays when necessary.