An information processing server (10; 40) comprising: a target vehicle data acquisition unit configured to acquire target vehicle data having traveling conditions of target vehicles and position information of the target vehicles on a map; an unstable behavior position recognition unit configured to recognize, based on the target vehicle data, an unstable behavior position on the map where at least one of the target vehicles exhibits unstable behavior, wherein the unstable behavior includes slip, a sudden deceleration or sudden change in steering angle, a lane deviation of the target vehicle, or an excessive approach of the target vehicle to a structure; and a storage processor configured to store a mesh and unstable behavior positions of the mesh in a storage database related to each other; characterized in that the server further comprises: an occurrence counting unit configured to measure an occurrence count of unstable behavior positions within a predetermined period in a mesh preset on the map; a mesh enlarging unit configured to, if the occurrence count of unstable positions in the mesh is less than a predetermined threshold, enlarge the mesh to include further unstable behavior positions on the map within the predetermined period such that the occurrence count of the unstable behavior positions is equal to or larger than the predetermined threshold; and a vehicle assistant unit (11k; 41d) configured to, when one of the target vehicles is traveling toward the mesh including the unstable behavior positions, provide vehicle assistance related to the unstable behavior positions in the mesh for the target vehicle, wherein the vehicle assistant unit (11k; 41d) is configured to change a vehicle assistance content depending on a size of the mesh. a target vehicle data acquisition unit configured to acquire target vehicle data having traveling conditions of target vehicles and position information of the target vehicles on a map; an unstable behavior position recognition unit configured to recognize, based on the target vehicle data, an unstable behavior position on the map where at least one of the target vehicles exhibits unstable behavior, wherein the unstable behavior includes slip, a sudden deceleration or sudden change in steering angle, a lane deviation of the target vehicle, or an excessive approach of the target vehicle to a structure; and an occurrence counting unit configured to measure an occurrence count of unstable behavior positions within a predetermined period in a mesh preset on the map; a mesh enlarging unit configured to, if the occurrence count of unstable positions in the mesh is less than a predetermined threshold, enlarge the mesh to include further unstable behavior positions on the map within the predetermined period such that the occurrence count of the unstable behavior positions is equal to or larger than the predetermined threshold; and a vehicle assistant unit (11k; 41d) configured to, when one of the target vehicles is traveling toward the mesh including the unstable behavior positions, provide vehicle assistance related to the unstable behavior positions in the mesh for the target vehicle, wherein the vehicle assistant unit (11k; 41d) is configured to change a vehicle assistance content depending on a size of the mesh.