The invention discloses a battery assembling device. The battery assembling device comprises a working platform, the working platform is provided with a gantry support, a first side of the gantry support is fixedly connected to a rolling assembly, the rolling assembly comprises a cylinder, a driven plate, a buffer plate, a roller mounting plate and a roller assembly, the cylinder drives a drivingplate, the driving plate is fixedly connected to the driven plate, two ends of the driven plate are fixedly connected to buffer springs, the buffer springs are connected to the buffer plate, the buffer plate is connected to the roller mounting plate, and the bottom of the roller mounting plate is rotatingly connected to multiple rollers. The cylinder drives the rollers to roll a battery so that the battery is fixed to the terminal so that the stress on the battery is uniform. The buffer springs are arranged between the battery and the cylinder so that the battery damage caused by the overlargeinstantaneous punching pressure is avoided as much as possible. The battery assembling device realizes firm assembling of a battery and does not damage the battery.