A driving assistance device comprising: a blind spot recognition unit that recognizes a blind spot of a driver in a progressing direction of a host vehicle; and a mobile object information setting unit that sets mobile object information including at least an assumed speed of a mobile object, as information on the mobile object having a possibility of appearing suddenly from the blind spot, a speed zone computation unit that computes a speed zone of the host vehicle within a map which is determined by a relationship between a speed of the host vehicle, and a distance of the host vehicle with respect to a reference position in a place forming the blind spot, in which there is a possibility that the host vehicle will come into contact with the mobile object when progressing in the progressing direction, based on the mobile object information set by the mobile object information setting unit; a brake avoidance condition computation unit that computes at least one of a brake avoidance condition according to which the host vehicle can avoid contact with the mobile object using a brake of the host vehicle and a brake avoidance condition according to which the mobile object can avoid contact with the host vehicle using a brake of the mobile object; and a target speed computation unit that computes a target speed of the host vehicle based on the speed zone, characterized in that a speed zone correction unit that corrects the speed zone within the map based on the brake avoidance condition computed by the brake avoidance condition computation unit; and the speed zone computation unit computes the speed zone by computing a condition that the mobile object can pass earlier than at least the host vehicle, based on the assumed speed of the mobile object. a blind spot recognition unit that recognizes a blind spot of a driver in a progressing direction of a host vehicle; and a mobile object information setting unit that sets mobile object information including at least an assumed speed of a mobile object, as information on the mobile object having a possibility of appearing suddenly from the blind spot, a speed zone computation unit that computes a speed zone of the host vehicle within a map which is determined by a relationship between a speed of the host vehicle, and a distance of the host vehicle with respect to a reference position in a place forming the blind spot, in which there is a possibility that the host vehicle will come into contact with the mobile object when progressing in the progressing direction, based on the mobile object information set by the mobile object information setting unit; a brake avoidance condition computation unit that computes at least one of a brake avoidance condition according to which the host vehicle can avoid contact with the mobile object using a brake of the host vehicle and a brake avoidance condition according to which the mobile object can avoid contact with the host vehicle using a brake of the mobile object; and a target speed computation unit that computes a target speed of the host vehicle based on the speed zone, characterized in that a speed zone correction unit that corrects the speed zone within the map based on the brake avoidance condition computed by the brake avoidance condition computation unit; and the speed zone computation unit computes the speed zone by computing a condition that the mobile object can pass earlier than at least the host vehicle, based on the assumed speed of the mobile object.