In a method and device to align phases of a first clock signal and a second clock signal, include a phase detector, a delay generator, and a controller. The phase detector is configured to generate a preceding signal and a succeeding signal with respect to the first clock signal to detect a relationship between phases of the first clock signal and the second clock signal. The delay generator is configured to delay the first clock signal when the second clock signal falls behind the succeeding signal with respect to the first clock signal. The controller is configured to determine whether the phases of the first clock signal and the second clock signal are aligned with each other according to the relationship detected by the phase detector.