A projection device including a processor circuit is provided. The processor circuit generates multiple warped feature points according to multiple first feature points and multiple second feature points. The processor circuit transforms a first mapping table into a second mapping table according to the warped feature points. The projection device projects a correction pattern to a projection screen. The correction pattern includes the first feature points. The processor circuit receives an image of the correction pattern projected to the projection screen that is captured by a 3D image capturing device, so as to obtain coordinate positions of the second feature points. The processor circuit calculates a viewer position according to the coordinate positions of the second feature points. The processor circuit generates an antiwarp image according to an input image and the second mapping table. The projection device projects the antiwarp image to the projection screen.