The present technology relates to a data processing device and a data processing method, which are capable of securing excellent communication quality in data transmission using an LDPC code. In group-wise interleave, an LDPC code in which a code length N is 64800 bits and an encoding rate r is 7/15, 9/15, 11/15, or 13/15 is interleaved in units of bit groups of 360 bits. In group-wise deinterleave, a sequence of the LDPC code that has undergone the group-wise interleave is restored to an original sequence. For example, the present technology can be applied to a technique of performing data transmission using an LDPC code.