The fruiting bodies of Paecilomyces japonica been used for an anticancer and immuno-stimulating agent as an oriental medicine, Antimutagenecity test with SOS chromotest and antioxidant test with NBT method were carried out using the concentrated culture broth, the extract of mycelia, and that of fruiting bodies. Among the sample extracts tested, the extract of fruiting bodies was most effective to antimutagenecity against the mutagens tested such as MNNG, ethidium bromide(EtBr), 2-aminofluorene(AF) and nitrofluorene(NF). Antimutagenic activity of all the extracts were very effective against mutagen, MNNG. When the extracts were added to certain concentration, antimutagenic activity was enhanced against mutagen, MNNG and NF. Antioxidant activity of the extract from fruiting bodies was highest. However, its activity was very low, compared to ascorbic acid.