MOBILE OBJECT CONTROL DEVICE, MOBILE OBJECT CONTROL METHOD, AND STORAGE MEDIUM

A mobile object control device includes a recognizer that recognizes a surroundings situation of a mobile object, and a controller that controls an acceleration and deceleration of the mobile object based on the surroundings situation recognized by recognize, and the controller sets a risk area at a first reference position based on an end of an obstacle present around the mobile object in a traveling direction of the mobile object when a predicted trajectory in which another mobile object is estimated to move and a future trajectory of the mobile object interfere with each other, and the length of a target area corresponding to the predicted trajectory in a predicted trajectory direction is equal to or larger than a predetermined length with respect to the target area difficult for the recognizer to recognize due to the obstacle, and controls at least the speed of the mobile object based on the set risk area.