A touch sensor device including a touch panel, the touch panel being formed by an insulator and having an outer surface that is exposed to an outer side and an inner surface opposite to the outer surface, the touch sensor device comprising: a plurality of electrodes arranged at the inner surface of the touch panel; and a control unit configured to, for each of the electrodes, detect a change in a capacitance generated at the electrode when a finger approaches the electrode and determine whether or not the touch panel has been touched from the change in the capacitance; wherein the control unit is configured to detect a maximum capacitance generated at the electrode in accordance with a size of the finger during detection of a touched state and set a first OFF determination threshold value, which is used to detect a non-touched state, to a value that is obtained by dividing the maximum capacitance by a predetermined set value, wherein the predetermined set value is set to be greater than one and to be smaller than or equal to two; the control unit is further configured to determine that the touching of the touch panel is a short tap when a time during which the touched state is detected is shorter than a first operation determination time, which is set in advance; and the control unit is further configured to, after the first touched state has shifted to the non-touched state in a condition in which the time during which the first touched state is detected is shorter than the first operation determination time and, upon detection of a second touch operation, detect and obtain a new maximum capacitance and then to determine whether or not a double tap has been performed on the touch panel when the control unit determines that the second touch operation has been performed in a condition in which a time during which the non-touched state is detected is shorter than a second operation determination time, which is set in advance, and the detected second touch operation is shorter than the first operation determination time, wherein a third OFF determination threshold value is used to determine that the first touched state of the double tap has shifted to the non-touched state and the third OFF determination threshold value is set to a value that is greater than the first OFF determination threshold value. a plurality of electrodes arranged at the inner surface of the touch panel; and a control unit configured to, for each of the electrodes, detect a change in a capacitance generated at the electrode when a finger approaches the electrode and determine whether or not the touch panel has been touched from the change in the capacitance; wherein the control unit is configured to detect a maximum capacitance generated at the electrode in accordance with a size of the finger during detection of a touched state and set a first OFF determination threshold value, which is used to detect a non-touched state, to a value that is obtained by dividing the maximum capacitance by a predetermined set value, wherein the predetermined set value is set to be greater than one and to be smaller than or equal to two; the control unit is further configured to determine that the touching of the touch panel is a short tap when a time during which the touched state is detected is shorter than a first operation determination time, which is set in advance; and the control unit is further configured to, after the first touched state has shifted to the non-touched state in a condition in which the time during which the first touched state is detected is shorter than the first operation determination time and, upon detection of a second touch operation, detect and obtain a new maximum capacitance and then to determine whether or not a double tap has been performed on the touch panel when the control unit determines that the second touch operation has been performed in a condition in which a time during which the non-touched state is detected is shorter than a second operation determination time, which is set in advance, and the detected second touch operation is shorter than the first operation determination time, wherein a third OFF determination threshold value is used to determine that the first touched state of the double tap has shifted to the non-touched state and the third OFF determination threshold value is set to a value that is greater than the first OFF determination threshold value.