The problems to be solved by the present invention are to provide an antenna which is applied to a wireless identification system wherein there is a long distance between a device to execute identification and a device attached to an object to be identified and which does not cause deterioration in aesthetic terms and covering of a meaningful symbol, and further to provide a wireless system using the antenna. According to the present invention, there are provided an antenna having a circularly polarizing function and a frequency equalizing function achieved by a grid structure having roughness and fineness around a feeding point and density which allows visible light to pass through, an RFID tag using the antenna, and an RFID system using the tag.