A seed substrate is placed to face a formation substrate, and then a gas containing silicon is introduced and chemical vapor deposition is performed. There is no particular limitation on a kind of a material used for the formation substrate as long as the material can withstand the temperature at which the reduced pressure chemical vapor deposition is performed. A group of silicon whiskers which does not include a seed atom can be grown directly on and in contact with the formation substrate. Further, the substrate provided with the group of whiskers can be applied to a solar cell, a lithium ion secondary battery, and the like, by utilizing surface characteristics of the group of whiskers.