A capacitive proximity sensor, comprising: a sensor electrode; an auxiliary electrode arranged in the vicinity of the sensor electrode; a detection circuit connected at least to the sensor electrode and operative to detect a capacitance value based on a capacitance on the connected electrode and to convert the capacitance value to a potential value; and a comparison/decision means, characterized by further comprising: a shield drive circuit; a change-over switch arranged to selectively switch between a first connection state of connecting the auxiliary electrode to the shield drive circuit and a second connection state of connecting the auxiliary electrode to the detection circuit or to make the auxiliary electrode open, grounded, or connected to a certain fixed potential; and the shield drive circuit for applying to the auxiliary electrode a potential equivalent to that on the sensor electrode, in the first connection state, wherein the comparison/decision means is operative to compare a first capacitance value from the detection circuit in the first connection state with a second capacitance value from the detection circuit in the second connection state to yield a comparison result, and to decide whether or not a sense target (A,B,C) locates within a range of a sense region based on the comparison result and the first or second connection state. a sensor electrode; an auxiliary electrode arranged in the vicinity of the sensor electrode; a detection circuit connected at least to the sensor electrode and operative to detect a capacitance value based on a capacitance on the connected electrode and to convert the capacitance value to a potential value; and a comparison/decision means, characterized by further comprising: a shield drive circuit; a change-over switch arranged to selectively switch between a first connection state of connecting the auxiliary electrode to the shield drive circuit and a second connection state of connecting the auxiliary electrode to the detection circuit or to make the auxiliary electrode open, grounded, or connected to a certain fixed potential; and the shield drive circuit for applying to the auxiliary electrode a potential equivalent to that on the sensor electrode, in the first connection state, wherein the comparison/decision means is operative to compare a first capacitance value from the detection circuit in the first connection state with a second capacitance value from the detection circuit in the second connection state to yield a comparison result, and to decide whether or not a sense target (A,B,C) locates within a range of a sense region based on the comparison result and the first or second connection state. a shield drive circuit; a change-over switch arranged to selectively switch between a first connection state of connecting the auxiliary electrode to the shield drive circuit and a second connection state of connecting the auxiliary electrode to the detection circuit or to make the auxiliary electrode open, grounded, or connected to a certain fixed potential; and the shield drive circuit for applying to the auxiliary electrode a potential equivalent to that on the sensor electrode, in the first connection state, wherein the comparison/decision means is operative to compare a first capacitance value from the detection circuit in the first connection state with a second capacitance value from the detection circuit in the second connection state to yield a comparison result, and to decide whether or not a sense target (A,B,C) locates within a range of a sense region based on the comparison result and the first or second connection state.