Abstract: A multi-rate transmission apparatus wherein components operate with a single clock from the outside and, even if the modulation system and the coding rate are varied arbitrarily by switching of the modulation operation mode similarly from the outside, transmission data can be allocated to modulation data and transmitted in response to the variation of the modulation system and the coding rate only with the clock signal from the outside. The multi-rate transmission apparatus includes a data processing section for reading in data with a bit width suitable for the modulation system, a coding unit for performing coding processing parallelly for the data read in by the data processing section, and a transmission section for transmitting the data, for which the coding processing has been performed, in response to the variation of the modulation system and the coding rate.