A key module and its manufacturing method are provided in the present invention. The steps of the method include: providing a mold; forming a key body having multiple opening portions on the mold; jostling a combination of a display body and an elastic body to the key body; and finally, tightly attaching the display body to the key body and stuffing the display body into the opening portions of the key body. Therein, the elastic body has a lower end formed with a contact block contacting a circuit board. By compressing, injecting or infusing a silicone rubber material or an elastic material into the opening portions, the gap located between the key body and the display body or between the key body and the elastic body is smaller than 0.01 mm. Thus, the appearance of the key module of the present invention is almost seamless.