PURPOSE: To obtain a sensor detection circuit which can effectively eliminate noise and exactly detect resistance change in a resistor connected in parallel to a capacitor in a system provided with a capacitor having a large capacitance.

CONSTITUTION: Provided are an alternating current power source 5 to detect resistance change in a resistor connected in parallel with a condensor by impressing alternating signal at a constant low frequency and a first wave formation circuit 8 to form wave by inputting the electric signal of the change appearing in the above alternating current at the time of resistance change generation. Also provided are a second wave formation circuit 9 to form wave by inputting alternating current signal impressed from the alternating current power source, an OR circuit 12 and an AND circuit 13 where the output signals from these wave formation circuits are input and a divider 18 or a subtractor where the output signals from these OR circuit and AND circuit are input and the phase change generated during the above resistance change is amplified.