A parking assistance device includes: a parking space candidate detection unit estimating positions of obstacles based on data of distance to the obstacles at both sides of a host vehicle, and detecting a parking space candidate at the sides of the vehicle; an image selection unit selecting two or more captured images in which an inner side surface of an obstacle adjacent to the parking space candidate is captured; a stereo image processing unit performing stereo image processing on the two or more captured images and calculating a three-dimensional point group of the obstacle; a position determination unit determining a position of the obstacle on the parking space candidate side based on the calculated three-dimensional point group; and a parking space correction unit correcting a position of the parking space candidate based on the determined position of the obstacle on the parking space candidate side.