Mobile architecture is the one of the main themes of architectural history of 20th century. These examines were explored by Jean Prouve, Buck Minster Fuller etc. The objectives of this research intend to examine the potential feature of so-called Mobile Space focusing on the double deck model that has a system of folding structure. To figure out the distinctive feature, a prototype was made to practice the utility of double deck mobile space. The prototype is able to transform into double deck when it sets up to the ground, and fold into single deck when it’s pulled by wrecker. Researching about the precedents of expanding-mobile-spaces, most examples were using horizontal extension system. This research examines exploring the way of expand the space in vertical direction with using folding structure. This system will mostly contribute land efficiency. In the prototype making process, a ground deck space was constructed using two-by-four method structure with 100 mm-glass-wool insulation between the panels. 40 mm by 40 mm steel frame was used as the folding structure of upper deck and enveloped by white membrane. Next phase, this prototype moved into practical use to find out some issues. Regarding those issues, folding system should be refined so to minimize down the setting up time. And structure frame of upper deck and the panels should reduce weight so to refine workability. Then the use of this double deck structure will be explored.