A method of detecting a contact state of resistive touch panel device includes measuring a potential at both ends of a first resistive film, as viewed in a first direction, as a first-film-potential. At this time, the both ends of the first resistive film are short circuited, and a predetermined current is applied between both ends of a second resistive film, as viewed in a second direction. The method further includes measuring a potential at the both ends of the second resistive film as a second-film-potential. At this time, the both ends of the second resistive film are short circuited, and the current is applied between the both ends of the first resistive film. The method further includes deriving distance information between two contact points of the first and the second resistive film, based on the first-film-potential and the second-film-potential.