A data transmission device and a data transmission method are provided. The data transmission device includes: a plurality of front-end modules associated with a plurality of antennas, respectively; and a controller configured to select a front-end module to be used for data communication from among the plurality of front-end modules, wherein the controller is configured to: determine a temperature of each of the plurality of front-end modules; and select, from among the plurality of front-end modules, a front-end module having a temperature lower than or equal to a threshold temperature and corresponding to a maximum received power of a receiving device, among received powers of the receiving device corresponding to the plurality of front-end modules, and wherein each of the received powers of the receiving device is obtained based on a specific absorption rate (SAR) requirement or a maximum permissible exposure (MPE) requirement of a corresponding front-end module.