A fungal strain which produced high levels of acid protease and amylase was isolated from the atmosphere for application to the manufacture of digestive enzme preparation. This study was carried out to elucidate its microbiological characteristics, environmental conditions for production of the enzymes, and relationships between the enzyme activity and acidity. 1. The isolate was identified as a fungal strain which belonged to Aspergillus niger by the manual of Rafer and Fennel, and was found to be a strain producing high levels of acid protease and amylase. 2. The optimal pH of tile enzymes produced by the strain were: protease, 2.0;, ${alpha}-amylase$, 4 to 5; and glucoamylase, 3 to 5. 3. The optimal culture conditions for production of the enzymes were: protease (at pH 2.5), 2 to 3 days incubation on wheat bran at $30^{circ}C$; ${alpha}-amylase$ and glucoamylase(at pH 3.0), 3 days incubation at $30^{circ}C$. 4. The production of acid protease and glucoamylase was increased approximately by 20 percent when 2 percent of corn starch was added to the wheat bran medium. 5. The addition of 0.3 percent ammonium sulfate to the wheat bran medium resulted in enhancing the enzyme production, especially of acid prctease.