A wiring substrate is provided. The wiring substrate includes a multilayer wiring structure and a stiffener. The multilayer wiring structure includes: a plurality of insulating layers; a plurality of wiring patterns; and a plurality of chip mounting pads which are electrically connected to the wiring patterns and on which a semiconductor chip is flip-chip mounted. The stiffener is provided on a portion of the multilayer wiring structure, which is outside of a mounting area on which the semiconductor chip is flip-chip mounted. A thermal expansion coefficient of the stiffener is substantially equal to that of the semiconductor chip.