Applications of the scanning plasma method (SPM) have been investigated for the surface treatment of polymeric materials such as polyethylene terephthalate and polypropylene. Using optical emission spectroscopy, it was found that a uniform plasma with about 140 mm in film width can be obtained due to the transportation effects of E × B drift in the presence of crossed magnetic field. The plasma treatment of polymeric materials by SPM induces the water contact angle to decrease, i.e., higher wettability, with increasing applied discharge voltage and decreasing the gas pressure. From the experimental results, it was found that SPM is very useful for the surface treatment of polymeric films because uniform and low-temperature surface treatment extending over a large area can be realized.