A capacitance detecting device comprising: a first capacitor and a second capacitor that are connected in series to each other between a power source and a detection electrode; a first switch that is connected between terminals of the first capacitor; a second switch that is connected between the first capacitor and the second capacitor; a third switch that is connected between terminals of the second capacitor; a control circuit that controls turning on/off the first switch, the second switch, and the third switch, is connected to a connection node between the first capacitor and the second switch, and detects a change in a capacitance of the second capacitor based on a potential of the connection node; said capacitance detecting device characterized by: a filter circuit that is connected to the connection node, transmits a potential of a frequency that is equal or less than a predetermined frequency and does not transmit a potential of a frequency that is more than the predetermined frequency, switching frequencies of the second switch and the third switch being less than the predetermined frequency; and a sample-and-hold circuit that is connected between the filter circuit and the control circuit, wherein the sample-and-hold circuit outputs a potential according to output of the filter circuit in a case where the second switch is controlled to be turned on, and holds and outputs a potential according to the output of the filter circuit obtained when the second switch is controlled to be turned off, until the second switch is controlled to be turned on at a next time, in a case where the second switch is controlled to be turned off. a first capacitor and a second capacitor that are connected in series to each other between a power source and a detection electrode; a first switch that is connected between terminals of the first capacitor; a second switch that is connected between the first capacitor and the second capacitor; a third switch that is connected between terminals of the second capacitor; a control circuit that controls turning on/off the first switch, the second switch, and the third switch, is connected to a connection node between the first capacitor and the second switch, and detects a change in a capacitance of the second capacitor based on a potential of the connection node; said capacitance detecting device characterized by: a filter circuit that is connected to the connection node, transmits a potential of a frequency that is equal or less than a predetermined frequency and does not transmit a potential of a frequency that is more than the predetermined frequency, switching frequencies of the second switch and the third switch being less than the predetermined frequency; and a sample-and-hold circuit that is connected between the filter circuit and the control circuit, wherein the sample-and-hold circuit outputs a potential according to output of the filter circuit in a case where the second switch is controlled to be turned on, and holds and outputs a potential according to the output of the filter circuit obtained when the second switch is controlled to be turned off, until the second switch is controlled to be turned on at a next time, in a case where the second switch is controlled to be turned off. a filter circuit that is connected to the connection node, transmits a potential of a frequency that is equal or less than a predetermined frequency and does not transmit a potential of a frequency that is more than the predetermined frequency, switching frequencies of the second switch and the third switch being less than the predetermined frequency; and a sample-and-hold circuit that is connected between the filter circuit and the control circuit, wherein the sample-and-hold circuit outputs a potential according to output of the filter circuit in a case where the second switch is controlled to be turned on, and holds and outputs a potential according to the output of the filter circuit obtained when the second switch is controlled to be turned off, until the second switch is controlled to be turned on at a next time, in a case where the second switch is controlled to be turned off.