A data processing device comprises: a displaying unit that displays various different screens; an operation receiving unit, which is layered on the displaying unit, that receives operation inputted from a user on the screen; an operation evaluating unit that evaluates contents of the operation by the user on the operation receiving unit; and a screen generating unit that generates a screen including a operation object, and changes the screen in response to the contents of an operation. The operation evaluating unit switches its mode from first mode of a default state to a second mode in response to a drag operation in the lengthwise direction of the operation object on the operation object on the screen, and evaluates an identical drag operation in a direction that is different from the lengthwise direction of the operation object to be different instruction operations between the first mode and the second mode.