The invention discloses an automatic calibrating device of a digital multimeter, which comprises a PC (Personal Computer), wherein the PC is respectively in line connection with a standard source and an image acquisition device, and the standard source is in line connection with the multimeter. According to the automatic calibrating device and a calibrating method of the digital multimeter, multimeter displayed measurement data are automatically read, identified and imported, the manual process that the multimeter displayed measurement data, recorded data and calculation errors are manually examined with electricity is replaced, the accuracy rate is increased, and additionally, the labor cost is reduced.