A manufacturing method of a multi-layered circuit board allows electronic parts to be mounted adequately and will not hamper performance of the electronic parts. A power terminal (pin) of an electronic part to be mounted on a surface of the multi-layered circuit board is inserted into a plated through hole to connect with a first conductive layer. A detecting section having a detecting hole which is formed coaxially with the through hole and whose diameter is larger than the through hole is provided on a second conductive layer on the back of the first conductive layer. A hole having a large diameter is formed by a tool along the through hole from the back while applying voltage between the second conductive layer and the tool. The depth of the hole is set based on the tool electrically conducting with the detecting hole. Unnecessary plate of the through hole may be removed by the large hole.