A semiconductor device includes a semiconductor chip mounted over a wiring substrate. A signal wiring for input for transmitting input signals to the semiconductor chip and a signal wiring for output for transmitting output signals from the semiconductor chip are placed in different wiring layers in the wiring substrate and overlap with each other. In the direction of thickness of the wiring substrate, each of the signal wirings is sandwiched between conductor planes supplied with reference potential. In the front surface of the semiconductor chip, a signal electrode for input and a signal electrode for output are disposed in different rows. In cases where the signal wiring for output is located in a layer higher than the signal wiring for input in the wiring substrate, the signal electrode for output is placed in a row closer to the outer edge of the front surface than the signal electrode for input.