Abstract: Disclosed is an adaptable/variable type modulation/demodulation apparatus. A physical layer transmission apparatus for adaptable/variable type modulation, the transmission apparatus including a classification unit to classify a bit stream according to a standard that is determined in advance after receiving the bit stream, an uncoded bit group unit to group the bit stream not to be LDPC-coded by a predetermined number of bits, an LDPC encoder to perform LDPC-coding of the bit stream, a coded bit group unit to group the coded bit stream by the predetermined number of bits, a quadrature amplitude modulation (QAM) unit to select a symbol coset using the coded bit groups; and a convolutional interleaver to perform convolutional interleaving of the symbol.