Phenazine 1-carboxylic acid (PCA) is an antifungal antibiotic isolated from a culture filtrate of Bacillus sp. B-6 producing an acyl CoA synthetase inhibitor. This antibiotic is reported as an inhibitor of an acyl CoA synthetase from Pseudomonas sp.. Bacillus sp. B-6 was resistant to PCA up to 350 ${mu}g/ml$. We investigated the mechanism of the resistance of Bacillus sp. B-6 to PCA. The rate of growth in a medium containing up to 100 ${mu}g/ml$ was as rapid as the PCA-free medium. At a PCA concentration of 300 ${mu}g/ml$, the growth rate was more than half that of the control. In this work, we purified acyl CoA synthetase from Bacillus sp. B-6 and found that this acyl CoA synthetase was much less sensitive to PCA than the acyl CoA synthetase from other source. These findings suggested that the insensitivity of Bacillus sp. B-6 acyl CoA synthetase plays an important role in the PCA resistance of this bacterium.