A prototype transition path editing tool for use in an immersive environment has been developed, which can be used for 3D keyframe animation authoring and editing of 3D transition paths. Authoring tools using 2D GUI is normally used to develop 3D animation. However, it is more direct to create 3D contents in a 3D space than in a 2D GUI. Therefore hand direct manipulation is employed to utilize body motion in the developed tool. Direct manipulation by hand is easy to understand and easy to use for rough positioning but it is not suitable for fine adjustments of virtual objects in an immersive environment because it is difficult to hold a hand at a fixed point without support in midair. A gearbox widget has been newly implemented to enable a user to adjust a value both roughly and minutely. In the immersive path editing tool, the developed widget and direct manipulation are combined to enhance efficiency of the immersive 3D authoring of keyframe animation.