In order to investigate the production of aflatoxin in various conditions such as pH, moisture and temperature, 27 smaples were inoculated with Aspergillus flavus, and in addition 3 smaples were inoculated with the mixture of Aspergillus flavus and Bacillus subtilis and cultured under the conditions such as $20^{circ}C$ and 30% moisture contents. The following results were obtained : 1) Aflatoxin production was the highest at pH 5.0 and relatively high at pH 7.0. Its production was decreased significantly when pH reached 9.0. 2) The yield of aflatoxin was shown comparatively high level at 30% moisture contens. The higher moisture contents was, the lower aflatoxin production was. 3) The highest level of aflatoxin production was at $20^{circ}C$, and comparatively high level was at $30^{circ}C$. However, its production was fairly low at $40^{circ}C$. 4) The highest crude aflatoxin production was 5,093ppm $(B_1,;1.912;ppm;;B_2,;0.521;ppm;;G_1,;2.119;ppm;;G_2,;0.541;ppm)$ at 30% moisture, pH 5.0 and $20^{circ}C$ and the lowest one 2.197 ppm $(B_1,;0.793;ppm;;B_2,;0.185;ppm;;G_1,;0.102;ppm;;G_2,;0.381;ppm)$ at 63% moisture, pH 9.0 and $40^{circ}C$ 5) When Aspergillus flavus and Bacillus subilis were cultured together under the conditions such as $20^{circ}C$ and 30% moisture, aflatoxin production was decreased by 27% comparing with the culture of Aspergillus flavus alone.