A radio-controlled lighting system includes: lighting devices each having a radio communication circuit; and a radio device which controls the lighting devices via radio communications. The radio device includes: an obtainer which obtains, for each of the lighting devices, variation information indicating variation in a received signal strength at either one of the radio device and a corresponding one of the lighting devices; a judging component which judges whether or not the variation indicated in the variation information satisfies a predetermined condition; a determiner which determines one or more of the lighting devices to be one or more of registration candidates when the judging component judges that the variation satisfies the predetermined condition; and a register which registers, as a target lighting device to be controlled, one of the lighting devices which is selected from the registration candidates.