A composition according to the present invention contains 100 parts by mass of a component (A) and 1-200 parts by mass of a component (B) and is solid at 25° C., the solid form being achieved at 25° C. without spray drying, impregnation into wax, or the like, and said composition is useful as an additive for a paint composition and an adhesive composition. The component (A) is an organic silicon compound represented by general formula (1), and the component (B) is at least one of organic silicon compounds represented by general formulas (2) and (3) (R1 and R2 represent, independently of each other, an alky group having 1-10 carbon atoms or the like, R3 and R4 represent, independently of each other, a divalent hydrocarbon group having 1-20 carbon atoms, m represents an integer from 1 to 3, R5 represents an alkyl group having 1-10 carbon atoms or the like, and R6 represents a divalent hydrocarbon group having 1-20 carbon atoms; however, an oxygen atom, a sulfur atom, etc., may be interposed between the aforementioned R5 and R6 and/or between carbon-carbon bonds in R6, and a hydrogen atom in R6 may be substituted by a halogen atom or the like.)