A wiring substrate includes a substrate with a first principal face and a second principal face. The first principal face has a first corner and first and second sides. The second principal face has a second corner corresponding to the first corner, and a third and a fourth side, respectively corresponding to the first and second sides. The substrate further comprising a first side surface connected to the first side, a second side surface connected to the second side, a third side surface connected to the third side, a fourth side surface connected to the fourth side, a first fracture part located between the first and third side surfaces to connect them, and a second fracture part located between the second and the fourth side surfaces to connect them. In the substrate's thickness direction, the length of the second side surface is smaller than the first side surface.