The present invention relates to a data processing apparatus and a data processing method which can improve the tolerance to errors of data. A demultiplexer 25 replaces, in accordance with an allocation rule for allocating code bits of an LDPC code to symbol bits representative of symbols, mb bits from among the code bits and sets the code bits after the replacement as symbol bits of b symbols. For example, when m is 12 and b is 1, where the i+1th bits from the most significant bit of the 12×1 code bits and the 12×1 symbol bits of one symbol are represented as bits bi and yi, replacement for allocating, for example, b0 to y8, b1 to y0, b2 to y6, b3 to y1, b4 to y4, b5 to y5, b6 to y2, b7 to y3, b8 to y7, b9 to y10, b10 to y11 and b11 to y9 is carried out. The present invention can be applied, for example, to a transmission system for transmitting an LDPC code and so forth.