A parking guidance device storing the information of length and width of a car is disclosed, which comprises: a central controller, a distance detector electrically connecting to said central controller for detecting the distances from obstacles, an image detector electrically connecting to said central controller for detecting the shape of a parking space, a two-axis rotating detector electrically connecting to said central controller for detecting the direction of said car, a human-machine operation interface electrically connecting to said central controller for inputting signals, and a car controller area network bus interface electrically connecting to said central controller for controlling wheel, engine and braking system, wherein said central controller integrates the information of distances and shape of said parking space, compares the same to the information of length and width of said car to gain a parking track, and makes the moving track of said car correspond with said parking track by controlling wheel, engine and braking system through the car controller area network bus interface.