Provided is a parking assistance device which enables information about free parking spaces of a parking lot to be timely, conveniently and effectively transmitted to automobile drivers. The parking assistance device comprises parking space detection modules, a mobile communication module and a data processing module. Each parking space in a parking lot is equipped with one parking space detection module used for detecting whether the parking space is occupied or not to generate parking space information. The mobile communication module is configured in an automobile and electrically connected with a GPS system in the automobile, and a driver sends parking request information through the mobile communication module. The data processing module is arranged in a parking lot management office, and is used for receiving the parking space information and the parking request information and sending parking feedback information to the mobile communication module.