The invention provides a composition containing a fruit body of Agaricus blazei murill or an extract of the fruit body, and an amino acid constituting the ornithine cycle or a salt thereof, wherein the pharmacological activities of the fruit body of Agaricus blazei murill or the extract of the fruit body and the amino acid constituting the omithine cycle or the salt thereof are increased synergistically. Such a composition can contain a fruit body of Agaricus blazei murill or an extract of the fruit body, and an amino acid constituting the ornithine cycle or a salt thereof in 10-100 parts by weight per 1 part by weight of the fruit body or the extract.