Rotatable antenna (RA) is a promising technology that exploits new spatial degree-of-freedom (DoF) to improve wireless communication and sensing performance. In this letter, we investigate an RA-enabled secure communication system where confidential information is transmitted from an RA-based access point (AP) to a single-antenna legitimate user in the presence of multiple eavesdroppers. We aim to maximize the secrecy rate by jointly optimizing the transmit beamforming and the deflection angles of all RAs at the AP. Accordingly, we propose an efficient alternating optimization (AO) algorithm to obtain a high-quality suboptimal solution in an iterative manner, where the generalized Rayleigh quotient-based beamforming is applied and the RAs' deflection angles are optimized by the successive convex approximation (SCA) technique. Our simulation results show that the proposed RA-enabled secure communication system achieves a significantly higher secrecy rate as compared to various benchmark schemes.