To provide a low-pass filter having a structure comprising a switched capacitor circuit with a very low cut-off frequency which is immune to the influence of a leakage current from an analog switch, and a semiconductor pressure sensor device using the low-pass filter.

The switched capacitor circuit is configured that during a clock pulse 1 of a 2-phase clock pulse, a first capacitor is charged with an input voltage, a second capacitor is discharged and a third capacitor is neither charged nor discharged, in the mean time, during a clock pulse 2, the second and third capacitors are charged by electric charge accumulated in the first capacitor which is connected to the second and third capacitors in parallel. As to a phase relation of the clock pulse 1 and the clock pulse 2, the clock pulse 2 rises leaving a short interval after an end of the clock pulse 1.