The present invention provides a forming method of forming a through electrode, in a second substrate joined on a first substrate having an electrode pad, to electrically connect a pattern to be formed on the second substrate to the electrode pad, the method comprising steps of detecting a position of a first mark formed on the first substrate and a position of a second mark formed on the second substrate in a state in which the first substrate and the second substrate are joined, determining, based on the position of the first mark and the position of the second mark detected in the detecting, a point to form the through electrode in the second substrate so as to electrically connect the pattern to the electrode pad, and forming the through electrode at the determined point.