Provided are an apparatus and a method for generating an identification key with improved reliability by: providing a plurality of resistances which are generated according to a random connection state between conductive layers of a semiconductor due to process variation of the semiconductor; discriminating a first group which has a resistance value greater than a first threshold value and less than a second threshold value among the plurality of resistances; and reading at least one resistance which does not belong to the first group out of the plurality of resistances and reading an identification key in the form of a digital value.