To provide a dipole antenna that maintains directional characteristics as an antenna and at the same time, can easily perform adjustment in impedance.

A pattern 15 for impedance adjustment is cut in the middle for gradually shortening a length (t), thus changing input impedance Z little by little for achieving the impedance matching between the dipole antenna 11 and an IC chip 17. The pattern 15 for impedance adjustment has a line shape with a narrow width, thus easily cutting the pattern 15 and hence easily adjusting the input impedance Z. Additionally, particularly making a dielectric substrate 12 large is not required, thus eliminating the need for making the size of the dipole antenna 11 large. Further, the directional characteristics in the dipole antenna 11 hardly fluctuate even if the length (t) is changed.