The invention discloses an electrode gap control method and device for numerical control electrolytic machining, and belongs to the field of electrode gap measurement. The electrode gap control method for numerical control electrolytic machining comprises the following steps: (1) measurement of an electrode gap: indirectly reflecting the electrode gap via the magnitude of an output signal of a Hall current sensor taken as a detection element of numerical control electrolytic machining current; (2) calibration of the electrode gap: calibrating the relation between the electrode gap of the numerical control electrolytic machining and the output signal of the Hall current sensor on line by means of a high-precision position control system of a numerical control electrolytic machining tool; (3) control of the electrode gap: constructing an electrode gap control system of the numerical control electrolytic machining on the basis of a numerical control system, the Hall current sensor and a converter. The invention further discloses the electrode gap control device for numerical control electrolytic machining. According to the method and the device, the efficiency of the numerical control electrolytic machining is increased, and the accuracy and stability of electrolytic machining are increased and enhanced.