A drive assist apparatus which performs driving assistance in a predetermined interval (L 0) having a gradient, comprising: average gradient information acquisition means for acquiring average gradient information of the predetermined interval (L 0); driving status information acquisition means for acquiring driving status information of a host vehicle; and gradient estimation means for estimating a gradient of a certain point within the predetermined interval (L 0) or an average gradient of a certain interval within the predetermined interval, based on the average gradient information acquired by the average gradient information acquisition means and the driving status information of the host vehicle that is acquired by the driving status information acquisition means, wherein the drive assist apparatus is adapted to perform driving assistance in the predetermined interval (L 0), using the gradient that is estimated by the gradient estimation means, wherein the driving status information acquisition means is adapted to acquire a longitudinal acceleration of the host vehicle, and wherein the gradient estimation means is adapted to estimate the gradient of the certain point within the predetermined interval (L 0) or the average gradient of the certain interval within the predetermined interval (L 0), based on the average gradient information acquired by the average gradient information acquisition means and the longitudinal acceleration of the host vehicle that is acquired by the driving status information acquisition means, characterized in that the gradient estimation means is adapted to estimate an average gradient from a starting end position of the predetermined interval (L 0) to a present position; and the gradient estimation means is adapted to estimate an average gradient from the present position to a terminating end position of the predetermined interval (L 0), based on the average gradient information acquired by the average gradient information acquisition means and the average gradient from the starting end position of the predetermined interval (L 0) to the present position. average gradient information acquisition means for acquiring average gradient information of the predetermined interval (L 0); driving status information acquisition means for acquiring driving status information of a host vehicle; and gradient estimation means for estimating a gradient of a certain point within the predetermined interval (L 0) or an average gradient of a certain interval within the predetermined interval, based on the average gradient information acquired by the average gradient information acquisition means and the driving status information of the host vehicle that is acquired by the driving status information acquisition means, wherein the drive assist apparatus is adapted to perform driving assistance in the predetermined interval (L 0), using the gradient that is estimated by the gradient estimation means, wherein the driving status information acquisition means is adapted to acquire a longitudinal acceleration of the host vehicle, and wherein the gradient estimation means is adapted to estimate the gradient of the certain point within the predetermined interval (L 0) or the average gradient of the certain interval within the predetermined interval (L 0), based on the average gradient information acquired by the average gradient information acquisition means and the longitudinal acceleration of the host vehicle that is acquired by the driving status information acquisition means, characterized in that the gradient estimation means is adapted to estimate an average gradient from a starting end position of the predetermined interval (L 0) to a present position; and the gradient estimation means is adapted to estimate an average gradient from the present position to a terminating end position of the predetermined interval (L 0), based on the average gradient information acquired by the average gradient information acquisition means and the average gradient from the starting end position of the predetermined interval (L 0) to the present position.