To provide a clock correcting circuit in an electronic exchange system with which a clock signal can be stably supplied regardless of variation in environmental conditions.

Respective parameters such as frequency or voltage of clock signal on a clock signal supply line from an electronic exchange are monitored and when each of parameters is distorted, in order to reduce such distortion, the terminal impedance of the clock signal supply line is controlled by changing the number of load units for control parallelly connected between the supply line and a power source side or ground side. Otherwise, this circuit can be configured by separating the distortion monitoring means of clock signal and the terminal impedance control means of the clock signal supply line and connecting both of the means by an information transmitting means as well.