1. A driving assistance apparatus used in a vehicle, comprising: a report section that performs a report to a driver of the vehicle; an arrangement acquisition section that acquires an obstacle arrangement around a parking region serving as a target in a parking-region driving operation, the parking-region driving operation being at least either a driving operation to cause the vehicle to enter into the parking region or a driving operation to cause the vehicle to exit from the parking region; an arrangement memory that stores a past obstacle arrangement around the parking region in a first parking-region driving operation at a past time, the first parking-region driving operation at the past time being a parking-region driving operation different from and previous to a second parking-region driving operation at a present time, the past obstacle arrangement having been acquired by the arrangement acquisition section in the first parking-region driving operation at the past time; and an obstacle specification section that specifies a non-stationary obstacle that is an obstacle not stationary around the parking region, based on a difference between (i) the past obstacle arrangement stored in the arrangement memory in the first parking-region driving operation at the past time, and ii) a present obstacle arrangement acquired by the arrangement acquisition section at the second parking-region driving operation at the present time, wherein the report section performs a report indicating presence of the non-stationary obstacle specified by the obstacle specification section; and wherein the arrangement memory stores a plurality of the past obstacle arrangements according to patterns classified depending on states in the parking-region driving operations, respectively; a pattern specification section is included to specify a pattern among the patterns depending on the states in the parking-region driving operations, respectively; and the obstacle specification section specifies the non-stationary object around the parking region based on a difference between (i) the present obstacle arrangement acquired by the arrangement acquisition section and (ii) the past obstacle arrangement according to the pattern specified by the pattern specification section among the past obstacle arrangements stored in the arrangement memory.