A (meth)allylsilane compound chemically bonded to various alcohol derivatives including polyol derivatives such as saccharides, is raw material used to cause a substrate to express functionalities such as a defogging property and separation characteristics for column chromatography, can be easily prepared, is easily purified, and is stable and easy to handle, and a functional material in which those functionalities are expressed, while silyl group-containing groups are conveniently carried at a high density on the surface of the substrate, by using the (meth)allylsilane compound as a silane coupling agent for silane-coupling to the substrate. The (meth)allylsilane compound includes a (meth)allylsilyl group-containing alkyl group or a (meth)allylsilylalkyl group-containing aralkyl group that is bonded to an alcohol derivative. In the functional material, the silane coupling agent is ether-bonded to surface hydroxyl groups exposed on a substrate through the surface hydroxyl groups by silane coupling to have an ether bond on the functional material.