To provide an antenna system capable of receiving electromagnetic waves with the best reception efficiency by providing plural resonating means set to respectively different resonance frequencies.

Concerning a duplication correspondent type IC card, a first resonance circuit 37 is constituted by connecting a resonance capacitor 31 to a loop antenna 32 loaded on a substrate 15, and a second resonance circuit 38 is constituted by connecting a resonance capacitor 34 to a loop antenna 33. The resonance circuits 37 and 38 are connected through a capacitor 35 and even when the distance of antennas 32 and 33 is extended, received power can be supplied to an electronic circuit 36. The first resonance circuit 37 is set to the resonance frequency coincident with the carrier frequency of electromagnetic waves radiated from a data writer/reader. The second resonance circuit 38 is set to the higher resonance frequency previously estimating a component to be lowered when two IC cards are overlapped.