A wiring substrate unit is provided. The unit includes: first and second wiring substrates, first and second input portions respectively formed in marginal portions of the first and second wiring substrates, and first and second output contact points respectively formed on one surfaces of the first and second wiring substrates. A through hole is formed in the first wiring substrate to correspond to the second output contact point; a cutout is formed either at a position adjacent to the first input portion of the marginal portion of the first wiring substrate or at a position adjacent to the second input portion of the marginal portion of the second wiring substrate; and one of the first and second input portions is exposed from the cutout.