A device that estimates the travel speed of a mobile body obtains a speed similarity of a travel speed associated with a road subject to estimation and a travel speed associated with each section of a map. The device also obtains an environment similarity degree of environment information corresponding to a section including the subject road and environment information corresponding to each section. A section similar to the section including the subject road is selected based on the total similarity degree, which is calculated based on the speed similarity and the environment similarity, to set the travel speed associated with the selected section as a travel speed of a corresponding time period on the subject road.