A method and apparatus detecting binary data, the apparatus includes an analog-to-digital (AD) converter converting the input analog signal into a digital signal; at least one binarization unit converting the digital signal into binary data; a viterbi decoder performing viterbi decoding to detect binary data from the digital signal; and a level detector receiving the digital signal, receiving at least two binary data from one of the viterbi decoder and the at least one binarization unit, and detecting and outputting a level value for the viterbi decoding from the digital signal when a number of the at least two binary data, which correspond to each other on a time axis and have the same values, is equal to or greater than a predetermined number. Accordingly, it is possible to more precisely detect binary data from an analog signal.