To provide a resin which can be used in coating/lining in situ, has satisfactory applicability, and is capable of forming a homogeneous coating film.

A solid molding is produced beforehand in a factory by mixing a liquid synthetic resin or inorganic material to be used for in-situ molding with additives and an aggregate and curing the mixture. The cured molding is processed into one or more forms selected among powdery, particulate, hollow, fibrous, and flaky forms. The resulting molding is mixed in situ with a liquid synthetic resin or an inorganic material and with additives and an aggregate to produce the objective resin, which is used in situ for coating/lining to form a coating film on a building, another construction, or an article.