PURPOSE: To measure the low resistance of a through-hole with high accuracy and high efficiency by connecting a current source and a voltage measuring instrument to the through-hole symmetrically and measuring a voltage applied to the through-hole by said voltage measuring instrument.

CONSTITUTION: A conductor layer 3 to which one end of the through-hole 2 is connected is formed on the reverse surface of an insulating substrate 1 and the constant current source 4 is connected between one end of the conductor layer 3 and through-hole 2. The voltage measuring instrument 5, on the other hand, is connected between the conductor layer 3 and through-hole 2. The connection position between the conductor layer 3 and voltage measuring instrument 5 is almost symmetrical with the connection position between the conductor layer 3 and constant current source 4. Consequently, the insulating substrate 1, constant current source 4, and voltage measuring instrument 5 are connected more easily than by a conventional four-probe method, and the low resistance of the fine through-hole is measured with high accuracy.