An automatic assembly jig adapted for assembling an electronic component and a case is provided. The jig includes a working platform, a carrier, a pressure exerting device and at least a gear. The working platform has a guiding rail. The carrier is disposed on the working platform and is slidably mounted on the guiding rail. The pressure exerting device is disposed above the working platform. The gear is disposed on the working platform and connected with the carrier, so as to drive the carrier moving along the guiding rail to the position under the pressure exerting device.