A determination device comprising: a sensor unit for detecting capacitances that vary in response to a touch or proximity of an operating object on or to an operation surface; a setting unit for setting a first threshold value based on a temporal change in variations in the detected capacitances; and a determination unit for determining, based on a result of comparison between the variations in the detected capacitances and the set first threshold value, whether the operating object is in a touch state relative to the operation surface; and an identification unit for identifying the operating object based on the variations in the detected capacitances, wherein the setting unit sets the first threshold value each time the identification unit identifies a new operating object, wherein the setting unit sets, based on a maximum value among peak values of the variations in the capacitances changing over time in response to movement of the operating object, the first threshold value less than the maximum value, the first threshold value being a value obtained by multiplying the maximum value by 0.8 and wherein the maximum value is decided to be a peak value at a time when the peak values stop increasing, characterised in that the identification unit specifies, based on a distribution of the variations in the detected capacitances in the operation surface, an area of a region where the identified operating object touches or is close to the operation surface, and when the area is greater than or equal to a predetermined value, the determination unit determines the operating object to be not in the touch state regardless of the result of comparison between the variations in the detected capacitances and the first threshold value. a sensor unit for detecting capacitances that vary in response to a touch or proximity of an operating object on or to an operation surface; a setting unit for setting a first threshold value based on a temporal change in variations in the detected capacitances; and a determination unit for determining, based on a result of comparison between the variations in the detected capacitances and the set first threshold value, whether the operating object is in a touch state relative to the operation surface; and an identification unit for identifying the operating object based on the variations in the detected capacitances, wherein the setting unit sets the first threshold value each time the identification unit identifies a new operating object, wherein the setting unit sets, based on a maximum value among peak values of the variations in the capacitances changing over time in response to movement of the operating object, the first threshold value less than the maximum value, the first threshold value being a value obtained by multiplying the maximum value by 0.8 and wherein the maximum value is decided to be a peak value at a time when the peak values stop increasing, characterised in that the identification unit specifies, based on a distribution of the variations in the detected capacitances in the operation surface, an area of a region where the identified operating object touches or is close to the operation surface, and when the area is greater than or equal to a predetermined value, the determination unit determines the operating object to be not in the touch state regardless of the result of comparison between the variations in the detected capacitances and the first threshold value.