The surface wave plasma (SWP) processing apparatus has been permitted to generate high-density and uniform plasmas via 2.45GHz microwave without external magnetic fields. To enlarge the processing area of the SWP apparatus, special configuration was investigated for a rectangular-type surface wave plasma apparatus that is equipped with multi dielectric-windows. The experimental investigation of the discharge characteristics of this apparatus with four windows (each size with 10cm × 10cm) has been carried out. To improve electron density uniformity, two methods have been surveyed. One is to insert quartz plates between metallic window frames of the chamber to make the boundary surface between plasma flat, and the other is to place parallel conductor plates on the window surface. The combination of these methods permits the reduction of nonuniformity of the spatial distribution of the electron density less than ± 6%.