A signal processing circuit is provided, which is suitable to be connected to a signal receiving conductor of a capacitive position detecting sensor, which has low power consumption and small circuit scale, and which allows setting of a small value as the capacitance value of a capacitor used for I-V conversion. After a receiving conductor is clamped to a predetermined potential by a clamp circuit, this receiving conductor clamped to the predetermined potential is connected to a capacitor circuit via a gate circuit. Thereby, a potential that changes corresponding to a position indicated by an indicator such as a finger is generated in the capacitor circuit, and a voltage signal generated in this capacitor circuit is converted to a digital signal to be output.