In a reception diversity system, a wireless apparatus includes an RF unit, analog signal processing unit, digital signal processing unit, and a control unit which controls the RF unit. The control unit operates only a predetermined system of systems while stopping the remaining systems for at least each intermittent operation period in intermittent reception operation of the RF unit, and stops all the systems in an intermittent stop period in the intermittent reception operation. The digital signal processing unit sets, in the RF unit, an initial reception gain estimated from an arbitrary past reception gain used in a past intermittent operation period as a first reception gain in a new system which is operated in accordance with arrival of a next intermittent operation period, thereby performing switching control of a plurality of systems which respectively demodulate received radio waves, and obtaining desired reception data. A control method for a reception diversity system is also disclosed.