The present invention provides an osteotomy device with an extracorporeal alignment component comprising a first body component, a second body component and an extracorporeal alignment component. The first body component has an upper guide edge for forming a cutting track. The second body component has a lower guide edge disposed below the upper guide edge. A guide slot is formed between the upper guide edge and the lower guide edge for guiding the saw blade to cut. The guide slot has a connecting member for connecting the upper guide edge and the lower guide edge. The extracorporeal alignment component has an engaging member and at least one aiming hole. The engaging member is engaged with the connecting member. The aiming hole is used to confirm the direction of cutting.