A first-collision predicting part determines if a possibility of a first collision, which happens between a human and a vehicle, is higher than a predetermined threshold. A first-collision-situation determining part determines a position of a head of the human and a relative speed of the head relative to the vehicle at a time of the first collision, when the first-collision predicting part determines the possibility of the first collision is higher than the predetermined threshold. A second-collision-situation estimating part estimates a collision situation of the head in a second collision, based on a determining result of the first-collision-situation determining part. An injury-degree predicting part predicts a degree of injury of the head based on an estimation result of the second-collision-situation estimating part.