A test mark is provided, for use in an inspection after a display panel, TAB
tapes,
and a flexible board have been connected together. Defective panels can be rejected
with high accuracy in the simple inspection, thereby mitigating the burden on the
microscopic inspection. At a predetermined distance from each of connection areas
for connecting a panel substrate, TAB tapes, and a flexible board, there are provided
test marks with at least one on each component. The electrical connection is tested
between each pair of the test marks to thereby determine whether the interconnection
is in a good state.