An input device for entering information matching a proximity state of an object, the input device comprising: a detecting unit (10-1 - 10-n) for generating a detection signal that changes according to a degree of proximity of the object, the detection signal having a reference value when no object is approaching, the degree of proximity of the object being indicated by a difference between the reference value and the value of the detection signal; a deciding unit for deciding according to a series of detection signals generated in the detecting unit (10-1 - 10-n), whether a change in the detection signal due to the proximity of the object is present by repeatedly calculating a first evaluation value, which indicates a magnitude of change in the detection signal in a first time; repeatedly deciding whether the first evaluation value is included in a first range, and if a state in which the first evaluation value is included in the first range continues for a second time or more, deciding that a change is not present in the detection signals along with the proximity of the object, and calculating the second time as a predetermined function that uses the difference value (S-BV) between the detection signal and the current reference value or acquiring the second time corresponding to the calculated difference value (S-BV) according to a predetermined data table in which a correspondence relationship between the difference value (S-BV) and the second time T2 is stipulated, wherein the larger the difference value (S-BV) is, the larger the value of the second time is, so that the deciding unit is more likely to decide that the change in the detection signal due to the proximity of the object is present; and a reference value updating unit for updating if the deciding unit decides that the change in the detection signal due to the proximity of the object is not present, the reference value, according to the detection signals generated in the detecting unit (10-1 - 10-n) by acquiring, as a new reference value, the detection signal, which is generated when it is decided in the deciding unit that a change is not present in the detection signals S along with the proximity of the object, or by acquiring, as a new reference value, the average of a series of detection signals in a state in which it is decided in the deciding unit that a change is not present in the detection signals along with the proximity of the object. a detecting unit (10-1 - 10-n) for generating a detection signal that changes according to a degree of proximity of the object, the detection signal having a reference value when no object is approaching, the degree of proximity of the object being indicated by a difference between the reference value and the value of the detection signal; a deciding unit for deciding according to a series of detection signals generated in the detecting unit (10-1 - 10-n), whether a change in the detection signal due to the proximity of the object is present by repeatedly calculating a first evaluation value, which indicates a magnitude of change in the detection signal in a first time; repeatedly deciding whether the first evaluation value is included in a first range, and if a state in which the first evaluation value is included in the first range continues for a second time or more, deciding that a change is not present in the detection signals along with the proximity of the object, and calculating the second time as a predetermined function that uses the difference value (S-BV) between the detection signal and the current reference value or acquiring the second time corresponding to the calculated difference value (S-BV) according to a predetermined data table in which a correspondence relationship between the difference value (S-BV) and the second time T2 is stipulated, wherein the larger the difference value (S-BV) is, the larger the value of the second time is, so that the deciding unit is more likely to decide that the change in the detection signal due to the proximity of the object is present; and a reference value updating unit for updating if the deciding unit decides that the change in the detection signal due to the proximity of the object is not present, the reference value, according to the detection signals generated in the detecting unit (10-1 - 10-n) by acquiring, as a new reference value, the detection signal, which is generated when it is decided in the deciding unit that a change is not present in the detection signals S along with the proximity of the object, or by acquiring, as a new reference value, the average of a series of detection signals in a state in which it is decided in the deciding unit that a change is not present in the detection signals along with the proximity of the object.