A space photovoltaic power generation system including a plurality of power satellites arranged in space, each of which converts electrical energy, into which sunlight has been photoelectric-converted, into a microwave, and transmits the microwave to an electric power base. The space photovoltaic power generation system divides the plurality of power satellites into a number of power satellite groups and adjusts the amount of phase adjustment to be made to a microwave which each of the plurality of power satellites included in each power satellite group will transmit so that a plurality of microwaves from the plurality of power satellites included in each power satellite group are in phase with one another. The beamwidth of the plurality of microwaves can be reduced without increasing the area of the aperture of a transmission antenna of each of the plurality of power satellites. If the plurality of microwaves transmitted from the plurality of power satellites included in each power satellite group interfere with microwaves transmitted from any other power satellite group, the beamwidth is reduced. To avoid the reduction in the beamwidth, each of the plurality of power satellites included in each power satellite group modulates the phase-adjusted microwave so as to generate an incoherent microwave so that the microwave does not interfere with other microwaves transmitted from any other power satellite group.