Device for detecting parking space and method thereof

A device for detecting a parking space of a smart parking assistant system (SPAS) is disclosed. A device for detecting a parking space includes: a signal pre-processing unit configured to filter reflection signals which are ultrasonic signals reflected and returned from a corner section of an obstacle, the ultrasonic signals being emitted from ultrasonic sensors attached to a vehicle; a pattern-based corner estimating unit configured to extract a crossing point of a plurality of circles having a plurality of measurement distances, which are collected from the reflection signals according to a movement of the vehicle as radiuses, estimate a reflection angle between a first line for bisecting a detection region within the detection region of the ultrasonic sensor, which has an attachment position of the ultrasonic sensor as a reference point, and a second line for connecting the reference point and the crossing point, and estimate the corner section of the obstacle based on the estimated reflection angle; and a parking space detecting unit configured to detect a parking space of the vehicle according to the estimated corner section.