A high speed data serial connection interface apparatus, CPRI transmitting and receiving methods thereof are disclosed. A high speed data serial connection interface apparatus according to the present invention includes: a data transmitter configured to count a continuous NCB of 0 or 1 in an input data block, select an LSI value, and perform up scaling on data in the block in accordance with the selected LSI value to transmit the data through an optical fiber in accordance with a CPRI (common public radio interface) protocol; and a data receiver configured to receive the data transmitted by the data transmitter, restore the LSI value from the received data, and perform down scaling on the received data in accordance with the restored LSI value to restore original data.