1. A method of tracking augmented reality content, comprising: recognizing an augmented reality marker from an input image and calculating a position and posture of the recognized augmented reality marker; calculating a position and posture of augmented reality content corresponding to the augmented reality marker by using the calculated position and posture of the augmented reality marker; synthesizing the augmented reality content with the input image by using the calculated position and posture of the augmented reality content, and displaying the synthesized image; updating the position and posture of the augmented reality content by using a 6-axis sensor when the augmented reality marker is not recognized in the input image; and synthesizing the augmented reality content with the input image by using the updated position and posture of the augmented reality content, and displaying the synthesized image.