To suppress noise components such as harmonic components of the fundamental component of an electromagnetic wave generated by a current flowing in a main coil functioning as an antenna, while suppressing attenuation of the fundamental wave component.An antenna coil unit comprises a main coil 41 and an auxiliary coil 42 which is insulated from the main coil 41 in an electric circuit manner and disposed at a position where an induction current is generated in the auxiliary coil by a magnetic field which is generated by a current flowing in the main coil 41. The auxiliary coil 42 is configured in such a way that a frequency deviated from a prescribed target frequency in harmonic components with respect to the fundamental component of an electromagnetic wave generated by the current flowing in the main coil 41 in a prescribed deviation direction just by a prescribed deviation amount, becomes a resonant frequency of the auxiliary coil. The deviation direction and the deviation amount are set in such a way that a phase of an AC current flowing in the auxiliary coil 42 is inverse to a phase of the harmonic component of an AC current flowing in the main coil 41.