The present invention provides a transmission device, a reception device, a test circuit and a test method, which enable internal parts of the circuit to operate at high speed, while performing inputting/outputting to/from a tester at low speed. The test circuit comprises a PLL 111 which divides the frequency of a test clock input from the tester to generate a PLL clock CKp1, a FIFO 113 which stores input data input from the tester on the test clock and outputs the data on the PLL clock CKp1, an encoder 114 which distributes bits of the input data, a driver 115 which transmits the output signal from the encoder 114 to the outside, a PLL 121 which divides the frequency of the test clock to generate a PLL clock CKp2, a decoder 124 which arranges the bits of the signal received by a receiver 123.