In order to expand its business, the company needs external sources of capital to finance the company activities. While using it, the company has the responsibility to repay the debt and the interest expense. Researchers suspect that gender diversity on board as a part of good governance reduces the probability of opportunistic behaviour and the cost of debt. Related to this problem, this study aims to examine the effect of female representation on boards and the cost of debt. Hypothesis testing uses samples from non-financial companies on IDX from 2015 to 2019. The result states that female director on boards has a significant negative effect on the cost of debt. It implies that gender diversity on boards matters. Further analysis shows that the negative relationship is contingent on education level. Overall, the study concludes that gender diversity on boards reduces the cost of debt.