The basic properties of the chamber wall cleaning in a reactive electron cyclotron resonance (ECR) plasma have been investigated using poly-Si wafers on the wall, to which a radio-frequency (RF) surface voltage was applied externally. The influence of the cleaning upon the processing plasma was also measured by a Langmuir probe. To keep the wall condition clean during the plasma processing, it was found that the ratio of cleaning on-time to off-time was an important factor as well as the potential difference between the plasma and the wall surface. The method of chamber wall cleaning proposed here was quite effective for keeping the initial wall condition constant without influencing the plasma parameters in the region of the processing too much.