Provided are a mobile information terminal, an information management device, and an information management system for mobile information terminals comprising the mobile information terminal and the information management device, with which it is possible to flexibly display also information that is voluntarily provided, for example, by a user, on map information. A navigation system of a vehicle acquires, by wireless communication, location information and post information that has been posted together with the location information, from an information management device of a management center in a state where the location information and the post information are associated. The navigation system controls the display of the acquired post information by a display device to be displayed in superposition in a location that is displayed upon the map information by the acquired location information.