Provided is a mobile transmitter and a transmitting method thereof. The mobile transmitter includes a transmission circuit and a control circuit. The transmission circuit selectively operates as a polar transmitter or a direct-conversion transmitter. The control circuit controls an operation of the transmission circuit based on the level of an output signal. The mobile transmitter operates as a direct-conversion transmitter using a linear power amplifier with a high dynamic range when it transmits a low-power signal. Also, the mobile transmitter operates as a polar transmitter using a switching power amplifier with a high power efficiency when it transmits a medium-power or high-power signal. Thus, the mobile transmitter according to the present invention can provide both the high power efficiency (i.e., the advantage of the switching power amplifier) and the high dynamic range (i.e., the advantage of the linear power amplifier). Consequently, it possible to increase the battery lifetime of a personal portable communication terminal and also to implement to a compound terminal that can satisfy a variety of communication standards with a high dynamic range.