To reduce burrs or cracks occurring on a wiring board when dividing a multi-piece wiring board having grooves for jointing lids.

In a multi-piece wiring board, a dividing grooves 2 is formed on the border between wiring board regions 1a, on one main surface of a matrix substrate 1 where the plurality of wiring board regions 1a having each a recess 3 at central parts are arranged vertically and horizontally. Between the dividing groove 2 and the recess 3 on one main surface of the matrix substrate 1, a groove 4 which is narrower than its interval but shallower than depth d1 of the recess 3 and depth d2 of the dividing grove 2 is provided. The matrix substrate 1 is divided well along the dividing groove 2, thereby the possibility of occurrence of burrs or cracks on a wiring board obtained by the division can be reduced.