This invention relates to as animation authoring system and an animation authoring method, to enable beginners to produce a three-dimensional animation easily and to solve input ambiguity problem in the three-dimensional environment. The animation authoring method according to the invention comprises the steps of: (a) receiving a plane route of an object on a predetermined reference plane from a user; (b) creating a motion window formed along the plane route and having a predetermined angle to the reference plane to receive motion information of the object on the motion window from the user; and (c) implementing an animation according to the received motion information.