Most of landmine detection robots proposed before have been strongly restricted to locomote because they have not been able to enter the minefield. So we have proposed a mine detection vehicle which can enter minefield with low-ground-pressure tires and scan landmines directly using GPR. Low-ground-pressure tire decrease ground contact pressure. And we are intended to make accurate map that point out the position where landmines are buried. The position of the vehicle is able to be observed with internal sensors (for the posture measurement) and external sensors (for the position measurement). However, when controlling the vehicle, the sampling time of external sensors and communication time from external sensors to the vehicle cannot be disregarded. Exact position of the vehicle must be predicted with dynamical model of the vehicle. We therefore propose dynamical model of the vehicle for low-ground-pressure vehicle. Based on experimental results, the dynamical model for low-ground-pressure vehicle is in consistency with acutual behavior of it.