Provided are a vehicle body assembling method and a vehicle body assembling apparatus which allow a simple configuration in the vicinity of the connecting portion between an upper jig and a lower jig and allow an increase in the efficiency of assembling work (welding work). A vehicle body assembling apparatus is equipped with a jig for supporting vehicle body components in a preassembled position, the jig comprising an upper jig and a lower jig which are connected to each other in at least two places. Each of the connection places is provided with a connecting means for fixing a three-dimensional coordinate position while allowing uniaxial turning. The vehicle body assembling apparatus is also equipped with a conveying means for conveying the upper jig which supports the vehicle body components, and reduces the load applied to the lower jig from the upper jig when connecting the upper jig to the lower jig.