A multilayered wiring substrate is constructed by stacking wiring layers 105, 108, 110, 112 and insulating layers 104, 106, 107, 109 in predetermined number, with at least one of the wiring layers being formed as a reinforcing wiring layer 103 whose thickness is 35 to 150 .mu.m arranged in one layer or plural layers. Also, the thickness of the reinforcing wiring layer is larger than that of the other wiring layers.