A wiring substrate includes signal input portions for inputting signals, a signal receiving portion that receives the signals input from the signal input portions, and a plurality of connection wires provides connections between the signal input portions and the signal receiving portion. The plurality of connection wires constitutes a connection wire group in which three connection wires are arranged overlapping one another with insulating layers being interposed therebetween, and the connection wire group is provided with a switching contact portion at which transmission paths of the signals respectively input to the connection wires are switched to the other connection wires.