The invention discloses a calibrating device for an AC and DC leakage current tester, which comprises an input device, a display device, a main control MCU (Microprogrammed Control Unit), an ADC (Analog Digital Conversion) voltage sampling unit, an DAC (Digital Analog Conversion) voltage reference generating unit, a DDS (Direct Digital Synthesis) AC waveform generating circuit, an input selector switch, an error amplifier, a time constant table, an AC and DC automatic range voltage meter, an automatic range resistor meter, an output selector switch matrix, an output power amplifier, an AC / DC true root mean square converter, an AC and DC voltage output module, an AC and DC current output module and an AC and DC small current simulating electronic load module. The calibrating device has higher frequency accuracy and stability without being externally connected with a computer; various functions are directly switched through the input device and the display device which are controlled bythe main control MCU, and various detection parameters are set; and the AC and DC automatic range voltage meter, the automatic range resistor meter, the time constant table, the AC and DC voltage output module, the AC and DC current output module and the AC and DC small current simulating electronic load module can be corrected in a soft correction manner.