In this paper, the authors propose vacant parking slot detection and tracking system that fuses the sensors of automatic parking system. The proposed system consists of few stages: parking slot detection, and parking slot marking tracking. The parking slot marking detection stage recognizes various types of parking slot markings using IR sensors. The parking slot occupancy classification stage identifies vacancies of detected parking slots using Infra sensor data. It is shown that the proposed method can recognize the positions and occupancies of various types of parking slot markings and stably track them under practical situations in a real-time manner.