The soil of Kwangneung area(Kyeunggi-Do) was inoculated directly into wheat-bran-media and after $3{sim}4$ days of incubation, a Penicillium species whose cellulase activity was 1011u/g was isolated. With the treatment of mutagenic agents an improved strain(cellulase activity: 1303u/g) was obtained. This strain was screened again by mono-spore isolation method. Finally a strain C8-14 (cellulase activity: 2351u/g) which had lesser spores than the wild strain was obtained.