Provided are a method and an apparatus for compression transmission of bus data including a plurality of bytes including upper bits and lower bits. The apparatus includes a comparator and an aligner. The comparator compares upper bits of a previous byte with upper bits of a current byte among the plurality of bytes. If the upper bits of the previous byte are identical to the upper bits of the current byte, the aligner compresses the bus data in a combination of a full-byte and a half-byte, by allowing the previous byte to be constituted with the full-byte having bits corresponding to the number of bits of the previous byte and allowing the current byte to be constituted with the half-byte excluding the upper bits of the current byte. Then, the aligner arrays the compressed bus data in a preset bus bandwidth to transmit to a slave device.