A step motor driving circuit is provided. An exemplary step motor driving circuit includes an input voltage source set, a reference voltage source, a voltage level shift unit, a logic unit, a reset voltage source, and an output voltage terminal. The input voltage source set provides an input voltage set. The reference voltage source provides a reference voltage. The voltage level shift unit raises one of the levels of the input voltage set to a level of the reference voltage. The logic unit receives the reference voltage and the input voltage set and outputs a control voltage. The reset voltage source outputs a reset voltage to reset the logic unit. The output voltage terminal receives the control voltage and outputs an output voltage.