Distribution of surface-wave-produced plasmas and profiles of electric field on a dielectric line under plasma production were measured using a surface-wave-plasma (SWP) applicator with a plasma area of 180×300 mm2. While the profile of the electric field in a direction of microwave propagation showed existence of a standing wave, the plasma, such as emission intensity or ion current, had a flat distribution. The electric field and the plasma had flat distribution in a direction perpendicular to the microwave propagation. Besides, they were hardly dependent on chamber pressure. Therefore, a uniform plasma is stably produced in the present SWP applicator and can be produced over a larger area.