A drive mode selection device for selecting a drive mode of an assistance device that assists a user by generating motive power using electric power from a battery, and that can be driven in a plurality of drive modes having different outputs, the drive mode selection device comprises a task information acquisition unit configured to acquire task information, which is information relating to a predetermined task to be executed by the assistance device; a remaining charge acquisition unit configured to acquire a remaining charge of the battery; a power estimation unit configured to estimate a power amount discrepancy on the basis of the task information and the remaining charge of the battery; and a mode selection unit configured to select the drive mode on the basis of the estimation result.