An information processing apparatus, comprising: sensor means (1; 70; 100) for generating a sensor output signal responsive to the three-dimensional coordinate position of a detection target in a monitor space by detecting a capacitance in the monitor space and for outputting the sensor output signal; position detector means for detecting the three-dimensional coordinate position of the detection target in the monitor space from the sensor output signal of the sensor means (1; 70; 100), the information processing apparatus being characterised by storage means for storing coordinate information identifying a three-dimensional space region set in the monitor space; determining means for determining whether the three-dimensional coordinate position of the detection target in the monitor space is contained in the three-dimensional set space region, based on the three-dimensional coordinate position of the detection target detected by the position detector means and the coordinate information stored in the storage means; and, output means for outputting determination results of the determining means wherein the three-dimensional space region is placed within the monitor space, and set in accordance with the external surface of the three-dimensional object elastically deformable under a pressing force, wherein the determining means determines that the three-dimensional object is under the pressing force of the detection target in response to a distance of the three-dimensional coordinate position of the detection target within the three-dimensional set space region from a border of the three-dimension set space region, and determines the intensity of the pressing force responsive to the distance from the border, and wherein the output means outputs an output signal responsive to a difference in the pressing force. sensor means (1; 70; 100) for generating a sensor output signal responsive to the three-dimensional coordinate position of a detection target in a monitor space by detecting a capacitance in the monitor space and for outputting the sensor output signal; position detector means for detecting the three-dimensional coordinate position of the detection target in the monitor space from the sensor output signal of the sensor means (1; 70; 100), the information processing apparatus being characterised by storage means for storing coordinate information identifying a three-dimensional space region set in the monitor space; determining means for determining whether the three-dimensional coordinate position of the detection target in the monitor space is contained in the three-dimensional set space region, based on the three-dimensional coordinate position of the detection target detected by the position detector means and the coordinate information stored in the storage means; and, output means for outputting determination results of the determining means wherein the three-dimensional space region is placed within the monitor space, and set in accordance with the external surface of the three-dimensional object elastically deformable under a pressing force, wherein the determining means determines that the three-dimensional object is under the pressing force of the detection target in response to a distance of the three-dimensional coordinate position of the detection target within the three-dimensional set space region from a border of the three-dimension set space region, and determines the intensity of the pressing force responsive to the distance from the border, and wherein the output means outputs an output signal responsive to a difference in the pressing force.