To prevent pull-in of an opposite phase in the case of in-phase synthesis.

An operation control means 9 activates a 2nd phase shift control means 8 for a prescribed time at a prescribed timing and then activates a 1st phase shift control means 7 so that a phase shift means 4 makes the phase of a 1st reception signal and the phase of a 2nd reception signal outputted from a reception means 3 to be matched with each other. At first, the operation control means 9 allows the 2nd phase shift control means 8 to control a phase shift of the phase shift means 4 so that a phase difference detected by a phase difference detection means 6 is converged to a 2nd phase difference region and then to control the phase shift quantity of the phase shift means 4 so that a phase difference detected by the phase difference detection means 6 is converged to a 1st phase difference region.