A determination device includes an input unit and a controller. The input unit receives information on a sidewalk area and information on a target object recognized in the sidewalk area. The sidewalk area exists between a position where a vehicle is present and a non-sidewalk area. The controller (i) divides the sidewalk area into a plurality of partial areas including at least a first partial area and a second partial area based on the information on the sidewalk area, the first partial area being closest to the vehicle among the plurality of partial areas, and the second partial area being adjacent to the non-sidewalk area, and (ii) determines, based on the information on the target object, at least one partial area among the plurality of partial areas to be a range where the vehicle is allowed to enter.