Although three-dimensional computer graphics (3DCG) is a powerful means to express ideas in a lively manner, it is difficult and time-consuming to create 3DCG content. One of the reasons is the gap between the two-dimensional (2D) manipulation space and the 3D modeling space. Meanwhile, the development of augmented reality (AR) applications has grown, with the mobile phone-based approach showing much promise. In this paper, we present a system for authoring animations of virtual objects in AR-based 3D space. The manipulation of the virtual character being superimposed on a marker is carried out by a finger in front of a camera on the backside of the mobile phone. This approach provides the user with the feeling of direct manipulation within the augmented 3D space. User testing has shown the effectiveness of our ARbased 3D animation authoring method, although we need to conduct further studies on the system implementation, including improvements to system response and finger motion detection in the depth direction.