the area of the first under surface pattern sb 1 and the area of the second upper surface pattern sa 2 is not equal to the area of the second under surface pattern sb 2 accordingly fig5 shows the area of the first upper surface pattern sa 1 being smaller than the area of the first under surface pattern sb 1 as an example hereinafter a description will be given with reference to a flowchart shown in fig6 of the disconnection inspecting method according to the second embodiment of the present invention first as shown in step s 1 the printed wiring board 3 as a target of a disconnection inspection is placed on the insulating sheet 2 next as shown in step s 2 the probe 4 is brought into contact with an upper surface pattern from upward the upper surface pattern being formed by the first upper surface pattern sa 1 and the second upper surface pattern sa 2 then in step s 3 a total capacitance between the reference conductor 1 and the upper surface pattern and between the reference conductor 1 and an under surface pattern formed by the first under surface pattern sb 1 and the second under surface pattern sb 2 is measured by the capacitance measuring instrument 8 twice or more with varying the thickness or the dielectric constant of the insulating sheet 2 then in step s 4 assuming that an area of the upper surface pattern is s 1 and an area of the under surface pattern is s 2 the area s 1 and the area s.