1. An object tracking device that obtains image data, detects an object, and tracks a target object comprising: one or more processors; and a memory coupled to the one or more processors and including instructions stored thereon that, when executed by the one or more processors, cause the object tracking device to: collate image data of a tracking object, which is a tracking target, with image data that has been obtained, and output information about a candidate region of the tracking object; determine an object region relating to the tracking object from the candidate region that is output; calculate depth information of the object; and set a depth range based on information about the object region that has been determined and the depth information that has been calculated, wherein the object region relating to the tracking object is determined based on an image region falling within the depth range that is set and the candidate region that is output.