Effect of mulberry tree powders on the antioxidant activity of submerged -liquid culture of mushrooms was investigated. Agaricus blazei (AB), Hericicum erinacium (HE), Pleurotus ostreatus (PO), Phellinus linteu (PL) and Paecilomyces japonicus (PJ) were cultured in a shaking incubator (200 rpm, $25^{circ}C$) for 7 days in culture media: 1) basal medium (BM) and 2) BM+1% mulberry tree powders (BMM). Hot water extracts from the submerged-liquid cultures of mushrooms and BMM were freeze-dried for the measurement of antioxidant activity, of which reaction mixture (25 mL: 10 mL of 0.2 M sodium phosphate buffer, pH 8.0; 4.5 mL distilled water; and 10.5 mL ethanol) contained 275 $mu$mol linoleic acid and one mg test sample. The reaction mixture was incubated in a shaking incubator (200 rpm, 4$0^{circ}C$) for 16 days. Peroxide value (POV) was measured for a period of over 16 days, and malonaldehyde (MA) was determined only for samples from the day 16 of incubation. Mycelial weight of mushroom strains cultured in BMM was greater than BM. The antioxidant activities of AB-cultured in BW (AB-BMM) and HE-cultured in BMM (HE-BMM) were superior to those of other mushroom strains-cultured in BMM or BM and of BMM. These results suggest that mulberry tree powders enhance the antioxidant activity of submerged-liquid culture of mushroom strains. The AB-BMM and HE-BMM were the most active cultures.