A data processing apparatus and a data processing method are provided. The method includes inputting q data streams, where each data stream includes Msymb complex-valued modulation symbols of one code word, and q and Msymb are integers greater than or equal to 1. The method also includes determining an l×l matrix used by the Msymb complex-valued modulation symbols included in each data stream, where the l×l matrix is one of an l×l identity matrix and a circulant matrix of the l×l identity matrix, and l is a quantity of transport layers. Additionally, the method includes performing, by using the determined l×l matrix, layer permutation mapping on the Msymb complex-valued modulation symbols included in each data stream.