There is offered a signal processing device of touch panel using an electrostatic capacity, which realizes improvement in noise tolerance and linear detection. An excitation pad, a first touch pad and a second touch pad are disposed on a substrate in a way that the excitation pad is interposed between the first and second touch pads. On the other hand, an alternating current power supply that provides the excitation pad with an alternating voltage through a wiring is provided on a sensor IC side of the signal processing device of touch panel. Also, there is provided an electric charge amplifier. The first touch pad is connected to a non-inverting input terminal (+) of the electric charge amplifier through an wiring, while the second touch pad is connected to an inverting input terminal (−) of the electric charge amplifier through a wiring.