An apparatus calculates a coefficient b that reflects a road slope condition of each section based on an altitude difference of both ends of each section stored in a memory, and identifies a carbon dioxide discharge amount that changes in proportion to the distance of each section by multiplying a distance D of each section by the coefficient b and another coefficient Ec. Further, the apparatus identifies a discharge amount that changes in proportion to a travel time of each section by multiplying a travel time T of each section and yet another coefficient a, and identifies a discharge amount based on an index that changes in proportion to the number of stops in each section by multiplying an index AEE by the coefficient Ec and still yet another coefficient c for performing a carbon-conscious routing between a start place and a destination.