1. An obstacle alarm device, comprising: a captured image acquisition unit for acquiring a captured image in which an image of a visual scene of a periphery of a vehicle has been captured; an attention-prioritized region setting unit for setting an attention-prioritized region to be the captured image; an outside region setting unit for setting an outside region to be outside the attention-prioritized region in the captured image; an object presence determination unit for determining whether or not an object is present in the outside region; a movement direction determination unit for determining a movement direction of the object; and a clear indication image output unit for causing a sign, which is turned on for a fixed duration of time and thereafter turned off, to be displayed at sequentially varying positions centerward from a side of the outside region where the object is present, within the attention-prioritized region displayed together with the outside region, in a case where the movement direction determination unit has determined that the object is moving toward the center of the attention-prioritized region.