To realize a multi-resonance characteristic decision system depending on the current amplitude/phase and the relation of position such as an interval between an antenna main conductor part and an auxiliary conductor part through the configuration of an external appearance realized to be one antenna without the need for a complicated matching circuit.

In the multi-resonance antenna where one end of a linear conductor 1 or 1a forming a main conductor connects electrically to a power supply source 6 built in a radio equipment case 8 and an earth 7 and a connection conductor 3 or 10 connects electrically to a connection part 5 or 12 on a linear conductor 2 or a cylindrical conductor 9 forming an auxiliary conductor, the linear conductor 1, the linear conductor 2 or the cylindrical conductor 9 are placed in parallel so that a distance between center axes of them is sufficiently shorter than the wavelength with respect to the antenna minimum degree resonance frequency.