1. An autonomous mobile device that executes a task upon autonomously moving to a destination, comprising: a known information storage device that stores information on known obstacles; a peripheral information acquisition device that acquires peripheral obstacle information; an identification device that identifies information on an unknown obstacle that is different from the known obstacles stored in the known information storage device, from the peripheral obstacle information acquired by the peripheral information acquisition device; an assessment information acquisition device that acquires assessment information related to the unknown obstacle when the information on the unknown obstacle is identified by the identification device; a scenario storage device that stores a plurality of action scenarios including a first action scenario which is defined to execute the task and is other than a second action scenario to cancel or continue the execution of the task; and a selection device that selects one action scenario among the plurality of action scenarios stored in the scenario storage device based on the assessment information acquired by the assessment information acquisition device; wherein the task is executed after the autonomous mobile device reaches a pre-registered via point on a travel path to the destination; the assessment information acquisition device acquires a plurality of types of assessment information, and upon selecting the action scenario based on the plurality of types of assessment information acquired by the assessment information acquisition device, the selection device selects the action scenario based on comprehensive information obtained by computing using at least one type of assessment information for each of the plurality of action scenarios; the assessment information acquisition device acquires, as the assessment information related to the unknown obstacle, at least two types of information from among: movement information related to the movement of the unknown obstacle; relative position information related to the relative position of the unknown obstacle relative to the autonomous mobile device; and attribute information of a zone where the unknown obstacle exists; and the relative position information is a score that is assigned to each of segments of the zone where the unknown obstacle exists based on the position of the autonomous mobile device.