A transmission device includes: an encoding unit; a modulation unit; a variable SF spread unit which performs spread with variable SF by control information A from a control unit; an IDFT unit which performs IDFT on the output from the spread unit; a GI insert unit; a parallel/serial conversion unit which converts the output from the GI insert unit into a serial data string; a digital/analog conversion unit; and an RF unit which transmits a signal from an antenna after converting the signal into a frequency band for transmitting an analog signal and controlling it to an appropriate transmission power. The control unit is configured to generate control information A for deciding the variable SF and input the information A into the variable SF spread unit and the RF unit. In the control information A, SF is modified according to the necessary transmission power.