Surface treatment of PEN (polyethylene naphthalate) film by pulsed atmospheric microplasma was experimentally investigated. Microplasma was generated with a pair of electrodes, covered with dielectric barrier, at relatively low discharge voltage of around 1 kV, and advantage of reducing the power and downsizing the entire plasma system. Electrodes were faced together with a spacer (thickness 100 um) in between. Streamers were generated between the electrodes, which generate various radicals and ions that could affect a target surface. We used Marx generator which generates negative pulsed for generating microplasma. Hydrophilization was confirmed measuring contact angle before and after the microplasma surface treatment with argon gas. Initial contact angle was about 73 degrees. As a result, the minimum contact angle was obtained at treatment time of 30 sec, discharge voltage of -1.3 kV, frequency of 24 kHz. Analysis by X-ray Photoelectron Spectroscopy (XPS) showed that decrease of C-H bond and increase of O=C bond and O-H bond.