A voltage trimming circuit includes a comparator, a code generator, nonvolatile storage device, a switch circuit, and a voltage generator. The comparator compares a reference voltage with a feedback voltage. The code generator generates a plurality of trimming codes for trimming the feedback voltage based on the comparison result of the comparator. If the feedback voltage is less than the reference voltage, the code generator adjusts up codes to increase the feedback voltage, from among the plurality of trimming codes and maintains down codes to decrease the feedback voltage, from among the plurality of trimming codes at an initial value. If the feedback voltage is greater than the reference voltage, the code generator adjusts the down codes and maintains the up codes at an initial value.