A touch panel device includes: an electrostatic capacitance touch panel of mutual capacitance type which includes transmission-side electrodes and reception-side electrodes; a detecting unit which detects a contact with the electrostatic touch panel and outputs contact information; and a detection signal variation calculating unit which calculates and outputs detection signal variations of the transmission-side electrodes and the reception-side electrodes based on the contact information. The touch panel device further includes: a variation distribution calculating unit which calculates and outputs a variation distribution of the detection signals based on the detection signal variations; and a determining unit which determines that an object contacting the electrostatic touch panel is a drop of water when a peak value of the variation distribution of the detection signals is a predetermined negative threshold or less.