Cycloalkyl silane compound such as cyclohexyl methyl dichlorosilane can be efficiently prepared by the photochemically induced hydrosilylation reaction. For example, an equimolar mixture of cyclohexene and methyl dichlorosilane with admixture of a catalytic amount of an alcoholic solution of, chloroplatinic acid, is irradiated at a temperature up to 70.degree. C. with ultraviolet light so that the hydrosilylation reaction takes place and proceeds almost to completeness without deactivation of the platinum catalyst to give the desired product in a yield of 90% or even higher.