The invention relates to an antenna and a radio-frequency identification tag equipped with the antenna. Disclosed is a tag antenna syntonic with a radio-frequency identification LSI chip of a capacitor element in a limited area and the radio-frequency identification tag equipped with the tag antenna. The radio-frequency identification tag has the antenna and the LSI chip connected to the antenna in parallel. The antenna is provided with: a feed terminal connected to the LSI chip, a loop antenna connected to the feed terminal and a bypass conductor as the bypass of the return circuit of the loop antenna, wherein the bypass conductor is located in a place having a distance S from the center of the loop antenna, and the size of the distance S is set such that the inductor has a prescribed inductance value due to the bypass conductor.