A tonneau cover device comprises a front tonneau cover that is comprised of boards and provided on a front side of a vehicle body, a rear tonneau cover that is comprised of a rollable type of member and provided on a rear side of the vehicle body, and a slide mechanism that moves a rear end of the front tonneau cover and a front end of the rear tonneau cover substantially vertically. Accordingly, there can be provided the tonneau cover device of a vehicle, which is provided so as to extend substantially horizontally above the baggage compartment at the vehicle-body rear portion, which can pull the tonneau cover upward according to the opening-closing movement of the back door, facilitate loading of baggage when the back door is opened, and improve appearances of the back door.