In this study, we propose a control technique for stabilizing the attitude of multicopters when one or motors develops a fault. Existing fault-tolerant multicopter control schemes attempt to secure the control force by tilting the principal axis or applying a control allocation method to the extra rotors in hexacopters and octocopters. However, these methods have the disadvantage of requiring additional mechanical devices for tilting and algorithms for fault detection and isolation. In this study, we propose a robust adaptive control method that overcomes these problems and can follow the commands of a multicopter in uncertain situations. In contrast to existing multicopter flight control methods, the proposed technique offers reliable performance against motion modeling errors and disturbances owing to its robustness to uncertainties. Simulations and flight tests verify that the proposed control technique can stabilize the attitude of a multicopter and follow the given attitude commands even in the event of faults.