The present technology relates to a transmission device, a receiving device, and a data processing method that enable bandwidth control over PLPs when one frequency band includes the plurality of PLPs. The transmission device determines the number of cells of a component to be transmitted by each of PLPs such that the number of cells in an entire physical layer frame including the plurality of PLPs matches a sum of the number of cells of the plurality of PLPs, and transmits a broadcast stream including the physical layer frame. The present technology can be applied to, for example, a system for transmitting a broadcast stream including a physical layer frame including a plurality of PLPs.