Abstract: One type of a prober for use in making measurement or aging of electric circuit elements and parts such as semiconductor integrated circuits is used for testing the electrical performance of semiconductor integrated circuit elements formed on the semiconductor substrate, and comprises a prober substrate of which thermal expansion coefficient is substantially same as that of the semiconductor substrate. The prober substrate has a plurality of leads at its center portion, said leads correspond to the pads of the semiconductor integrated circuit element, each lead has a contact to abut on the corresponding pad, and said prober substrate has conductive layers formed thereon each having one end extending to said contact and other end terminating in the vicinity of the circumference of the prober substrate.