A touch panel apparatus includes a first substrate including a first conductive film, a second substrate including a second conductive film, a first terminal, a second terminal, a third terminal, and a fourth terminal respectively provided on the second substrate, and a controller. The controller calculates a potential difference between a measured potential and a reference potential of each of the first and second terminals with connecting the first and second terminals to the power source and the third and fourth terminals to the ground potential, and a potential difference between a measured potential and a reference potential of each of the third and fourth terminals with connecting the second and third terminals to the power source and the first and fourth terminals to the ground potential, determines a potential difference having a largest value, and calculates a relationship between two contact points based on the determined potential difference.