Provided are a reference voltage training device and a method thereof. The reference voltage training device includes a comparator configured to compare a toggle signal with a reference voltage and output a comparison signal, a duty cycle detector configured to check a duty ratio of the comparison signal, and a reference voltage level changing unit configured to fix the reference voltage when the duty ratio meets a predetermined condition and to change a level of the reference voltage when the duty ratio does not meet the predetermined condition. The comparator outputs a changed comparison signal using the changed reference voltage.