To understand the mechanism of surface processing using atmospheric-pressure nonequilibrium plasma jets, we measured thevibrational and rotational temperatures in the plasmas by optical emission spectroscopy. Plasma was excited using a high-frequency pulsed power supply, using a gas mixture of Ar (20 L/min) and N2(0.1 to 0.5 L/min) as the plasma gas, andchanging the flow rate of N2gas at an input power of 100 W and plasma frequencies of 5 and 10 kHz. The measuredvibrational and rotational temperatures in plasma were approximately 0.18 to 0.26 eV and 0.21 to 0.28 eV, respectively. Wealso carried out a plasma surface processing of polyethylene terephtalate film to measure the changes in water contact anglebefore and after the processing. We found a monotonic decrease in the contact angle of the processed poly(ethyleneterephtalate) (PET) film as plasma rotational temperature increased. It is concluded that the hydrophilicity of the PET surfaceincreases with plasma rotational temperature.