To diversify the flavor and taste of miso, white mutants of Aspergillus sojae were derived by UV irradiation, and a favorite strain No.601 thus obtained was subjected to comparison with a commercial miso koji mold BF-1 on miso fermentation. Enzymatic activities of No.601 were as follows: Activities of a-amylase (α-Amy) and glucoamylase (S-Amy) were 1/21 and 1/14, respectively, as compared to those of BF-1, and activities of pectin lyase (PEL), cellulase (CMCase), β-glucosidase (β-Gluco) and glutaminase (GLT) were 2-6 times as high as those of BF-1. No.601 strain showed lower consumption ratio of total sugar during koji making. No.601 miso contained smaller amount of direct reducing sugar (DRS) and larger amount of total sugar (TS) than BF-1 miso. The color index x of No.601 miso was higher than that of BF-1 miso, though the Y (%) value was somewhat lower and hardness was lower. No.601 miso was well evaluated on brightness, clearness and gloss in color, characteristic flavor, favorite taste and softness in texture, though it was somewhat bronwned.+