A three-dimensional (3D) interactive device and an operation method thereof are provided. The 3D interactive device includes a projection unit, an image capturing unit, and an image processing unit. The projection unit projects an interactive pattern to a surface of a body, so that a user performs an interactive trigger operation on the interactive pattern by a gesture. The image capturing unit captures a depth image within an image capturing range. The image processing unit receives the depth image and determines whether the depth image includes a hand region of the user. If yes, the image processing unit performs hand geometric recognition on the hand region to obtain gesture interactive semantics. According to the gesture interactive semantics, the image processing unit controls the projection unit and the image capturing unit. Accordingly, the disclosure provides a portable, contact-free 3D interactive device.