A mobile terminal device comprising: a first main display unit that has a first display screen; a second main display unit that has a second display screen which can provide a display equivalent to said first display screen, said second main display unit being connected so as to be capable of being juxtaposed to said first main display unit; a control unit adapted to perform overall control; a display state detection unit that is adapted to detect whether or not both said first display screen and said second display screen are in a state where simultaneous display is possible; an operation target screen selection unit that is adapted to execute a function to select, among said first display screen and said second display screen, a screen that is a target for operation; and an operation target screen switching icon display unit that is adapted to execute a function to display an operation target screen switching icon (70A, 70B) at least on the screen selected by said operation target screen selection unit, when said display state detection unit detects that both said first display screen and said second display screen are in a state in which display is possible, wherein said operation target screen selection unit is adapted to switch selection of an operation target screen when said operation target screen switching icon (70A, 70B) is selected; said first main display unit and said second main display unit are connected by a hinge unit; said second main display unit comprises a third display screen on a rear side of said second display screen; when said display state detection unit detects a change from a folded state to an open state, the mobile terminal device is adapted to switch automatically, from said third display screen to said second display screen, the display content of an application that has been displayed on said third display screen, and said operation target screen switching icon display unit is adapted to generate said operation target screen switching icon (70A, 70B) on said second display screen; and when said display state detection unit detects that said first main display unit and said second main display unit are in a folded state, the mobile terminal device is adapted to stop displaying of both said first display screen and said second display screen, and to display, on said third display screen, display content of an application. a first main display unit that has a first display screen; a second main display unit that has a second display screen which can provide a display equivalent to said first display screen, said second main display unit being connected so as to be capable of being juxtaposed to said first main display unit; a control unit adapted to perform overall control; a display state detection unit that is adapted to detect whether or not both said first display screen and said second display screen are in a state where simultaneous display is possible; an operation target screen selection unit that is adapted to execute a function to select, among said first display screen and said second display screen, a screen that is a target for operation; and an operation target screen switching icon display unit that is adapted to execute a function to display an operation target screen switching icon (70A, 70B) at least on the screen selected by said operation target screen selection unit, when said display state detection unit detects that both said first display screen and said second display screen are in a state in which display is possible, wherein said operation target screen selection unit is adapted to switch selection of an operation target screen when said operation target screen switching icon (70A, 70B) is selected; said first main display unit and said second main display unit are connected by a hinge unit; said second main display unit comprises a third display screen on a rear side of said second display screen; when said display state detection unit detects a change from a folded state to an open state, the mobile terminal device is adapted to switch automatically, from said third display screen to said second display screen, the display content of an application that has been displayed on said third display screen, and said operation target screen switching icon display unit is adapted to generate said operation target screen switching icon (70A, 70B) on said second display screen; and when said display state detection unit detects that said first main display unit and said second main display unit are in a folded state, the mobile terminal device is adapted to stop displaying of both said first display screen and said second display screen, and to display, on said third display screen, display content of an application.