To provide an onboard TV diversity system which can select the optimal reception signal for TV reception from reception signals by controlling a system so that the reception signal of the largest level is selected among plural phase synthesis signals and reception signals.

A phase compositing means 4 generates the four types of reception signals on reception signals RA and RB that TV antennas 2A and 2B receive, the in-phase composite signal RPA and an opposite phase composite signal RPB, which are obtained by phase-compositing the reception signals RA and RB to the in-phase and the opposite phase. A selection means 5 sets switches sw1-sw4 from a brake state to a make state based on a selection control signal CS supplied from a reception means 6, and selects one signal from the reception signal RA, the in-phase composite signal RPA, the opposite phase composite signal RPB or the reception signal RB and supplies it to a reception means 6 as a reception signal SR. The reception means 6 supplies a comparison signal HO corresponding to the highest level to a selection control means 8.