By using a Langmuir probe, the electron energy distribution function (EEDF) is measured in inductively coupled plasma discharges in N2/Ar mixtures at 200W rf powers. In pure N2 discharges a Maxwellian EEDF is observed. When the mixing ratio of Ar increases, the distribution of high-energy electrons evolves with a dierent trend from that of low-energy electrons, resulting in an apparent "two temperature structure" of the EEDF We discuss this non-Maxwellian EEDF and its effect on the measurement and the interpretation of "electron temperature" by both the probe and line ratio technique.