PURPOSE: To present the matching control method of an RF generator used for a semiconductor manufacture device or the like with high efficiency and stable quality by turning reflected power to zero in a short time and maximizing power supplied to a load by most effectively controlling the impedance matching of the RF generator used for sputtering or the like.

CONSTITUTION: Input power Pi and reflected power Pr detected by a power detector in an RF power source is inputted to a Kr arithmetic circuit 1 of an impedance matching box and an output Kr is obtained. The Kr is inputted to a CPU after receiving A/D conversion at an A/D converter 3. While referring to a memory 9, the CPU 8 sets the matching position and limiter set value of a variable condenser, next drives driving motor M1 and M2 through a motor control circuit 7 and obtains matching.