Because a route selection model for traffic demand prediction of selecting a route from among travel routes in probe data cannot include other routes than the travel route in the probe data, it is not possible to predict a traffic volume on the route that has not been traveled. A traffic-volume prediction device includes a simple-network creation device that makes a simple network connecting principal intersections extracted from travelling loci in the collected probe data, a model creation device that determines a utility between the principal intersections based on the data of the travelling loci and calculates a selection probability for each principal intersection based on the utility, and a traffic-volume assignment device that distributes a traffic volume to the routes between the principal intersections according to the selection probability and uses the traffic volume for each route candidate to be a traffic demand prediction object.