1. An obstacle alert device comprising: a captured image obtainment unit that obtains a captured image of a scene of the periphery of a vehicle; a target captured image generation unit that generates a target captured image based on the captured image; an object presence determination unit that determines whether or not an object is present in an outside region that is on an outer side of the target captured image; a movement direction determination unit that determines a movement direction of the object in the outside region; and a notification image output unit that, in the case where the movement direction determination unit has determined that the object in the outside region is moving toward the center of the target captured image, sequentially displays a plurality of indicators, that appear for a set amount of time and then disappear, in different locations of the target captured image, starting with the side having the outside region in which the object is present and moving toward the center of the target captured image, and repeats this display while displaying the plurality of indicators in positions where the indicators partially overlap with each other, with the indicator displayed later being displayed over the indicator displayed immediately previous thereto at the areas where the indicators overlap.