The invention is to provide a novel .beta.-glucosidase and a gene that codes for the enzyme, and to develop a technique of utilizing the .beta.-glucosidase or a composition that contains the enzyme for processing plants or plant-derived substances.According to the invention, there are provided a novel enzyme showing a .beta.-glucosidase activity and derived from filamentous fungi of the genus Acremonium, a gene that codes for the enzyme, a method of using the gene for expressing .beta.-glucosidase, an enzyme composition that contains .beta.-glucosidase, and a method of processing plants or plant-derived substances with the enzyme or the enzyme compositions.