1. A three-dimensional interactive device comprising: a projection unit projecting a first interactive pattern to a surface of a body, such that a user performs an interactive trigger operation on the first interactive pattern by a gesture, wherein the first interactive pattern is projected within a projection range; an image capturing unit capturing a depth image within an image capturing range, wherein the image capturing range covers the projection range; and an image processing unit connected to the projection unit and the image capturing unit, the image processing unit receiving the depth image and determining whether the depth image comprises a hand region of the user, if yes, the image processing unit performs hand geometric recognition on the hand region to obtain a gesture interactive semantics, and the image processing unit controls the projection unit and the image capturing unit according to the gesture interactive semantics.