In order to achieve inner wall surface treatment of glass tube of micrometer and gas decomposition flowing through a small diameter glass tube, a micro-plasma is useful. We have developed a new method for producing a micro-plasma in order to apply to the surface treatment and micro-plasma CVD on the inner wall surface of a micro-glass tube at atmospheric pressure. The plasma is produced by using a coaxial microelectrode to which RF impulse is applied. We have elucidated fundamental characteristics of the discharge and optimized the electrode configuration. We find that breakdown voltage can be decreased with a decrease in the diameter of the inner electrode. We also clarified the effect of gas species and flow rate on the discharge. (c) 2005 Elsevier B.V. All rights reserved.