The present invention is a wheelbase for a movable structure, comprising: a first frame unit connected to either a front wheels or a rear wheels; a second frame unit connected to the other of the front wheels or the rear wheels and located below or above the first frame and coupled to the first frame (an accommodation space being formed between the first frame unit and the second frame unit); a slider unit located within the accommodation space and coupled to either the first frame unit or the second frame unit; a driving unit located at a longitudinal cross sectional surface of the other of the first frame unit or the second frame unit so as to generate a driving force; and a driving-force-transmitting unit for interconnecting the driving unit and the slider unit to transmit the driving force to the slider unit. The driving unit moves the slider unit along the lengthwise direction of the other of the first frame unit or the second frame unit so as to adjust the spacing between the front wheels and the rear wheels. The thus-configured wheelbase for a movable structure may adjust the spacing between wheels in order to achieve a suitable state of the movable structure.