This communication device has a phase-modulation spatial light modulator; and a control unit which causes, during one frame time interval, the phase-modulation spatial light modulator to operate with first and second operation patterns. In a predetermined period within the one frame time interval, the first operation pattern includes a first light transmittable interval during which first signal light can be output, and a first pause interval during which the first signal light cannot be output whereas the second operation pattern includes a second light transmittable interval during which second signal light can be output, and a second pause interval during which the second signal light cannot be output. The first and second light transmittable intervals are each longer than a half of the predetermined period. The second pause interval is present within the first light transmittable interval, and the first pause interval is present within the second light transmittable interval.