A diversity receiving device includes a processing circuit in which receiving units, AFC and synchronizing units, and demodulating units for a plurality of systems are connected, received signal intensity detecting units 104 and 105 that detect the intensities of output signals of the respective receiving units so as to output reception intensity detection signals, a control unit that determines to select one system as a synthesis pattern of demodulation signals based on a predetermined judgment criterion according to the respective reception intensity detection signals or to select a plurality of systems so as to add demodulation signals and outputs a plurality of clock interruption control signals requesting the interruption of a clock supply to unselected systems and synthesis pattern selection signals designating a synthesis pattern of demodulation signals of the selected system, a plurality of clock supply units that interrupt the clock supply to the AFC and synchronizing units and the demodulating units of the unselected systems according to the clock interruption control signal, and a synthesizing unit that synthesizes demodulation signals of the selected system according to the synthesis pattern selection signals.