Disclosed herein is a data identification method for identifying, from within a readout signal from a recording medium on or in which user data of k bits are recorded using a recording modulation code wherein m bits from among n bits which compose one codeword have a value of “1” while the remaining n-m bits have another value of “0”, the data, n and m being integers including, a first step of delimiting the readout signal in a unit of a codeword and adding, with regard to one of the n-bit codewords obtained by the delimiting, an amplitude of the readout signal of the bits of “1” to 2ˆk different codewords which may possibly be recorded and setting results of the addition as evaluation values, and a second step of finding a maximum value among the 2ˆk evaluation values and outputting the maximum value as an evaluation result.