Abstract: A system for mounting circuit components on a circuit substrate, including a supplying device which supplies the components, a supporting device which supports the substrate, component holders each for holding one component, a revolving device which revolves the holders around an axis line, and stops the holders at a component receiving position and a component mounting position predetermined on the locus of revolution of the holders, a moving device which includes a support member supporting the revolving device and moves the support member, thereby moving the revolving device to a desired position in a plane facing the supplying device and the supporting device, an elevating and lowering device which is supported by the support member and which elevates and lowers each holder at the receiving and mounting positions, a first control device which controls each holder to receive, at the receiving position, the component supplied from the supplying device and mount, at the mounting position, the component on th