This invention relates to a data decoding apparatus and data decoding method which perform maximum likelihood decoding by means of a simple construction. The apparatus includes, an equalizer device, a binary conversion device, a temporary identification device, a correction device, an analog to digital converter device, a digital equalizer device and an identification device. The data decoding method includes that, when a logic level inversion timing during one clock interval is detected from an input signal, a provisional identification result of identifying the input signal is corrected by effectively one clock identification error, the number of state transitions which can be obtained from the input signal is limited based on this corrected provisional identification result, and the most probable state transition of these limited state transitions is detected to output an input signal identification result. |