PROBLEM TO BE SOLVED: To find a Cordyceps sinensis expressing excellent activity depending on silkworm species, even for a Cordyceps sinensis of the same strain.SOLUTION: An immunostimulator, a cancer cell proliferation inhibitor, an anti-inflammatory agent, and an antioxidant include a Cordyceps sinensis cultured by using KOISHIMARU as a silkworm species, and by using KOISHIMARU as a host, or include an extract of the Cordyceps sinensis as an active ingredient.