A method for determining the planting ball number of a camera module is provided. The camera module includes a substrate and a chip. The substrate includes an opening and a plurality of contact pads. The opening of the substrate has four rims. The method includes the following steps. Firstly, an image pickup device is used to detect an average contact pad distance of the distances from four specified contact pads of the substrate to the image pickup device. Then, a smallest opening distance among four opening distances from the four rims to the image pickup device is acquired. Then, plural actual contact pad distances from all contact pads to the image pickup device are acquired. The planting ball number for each contact pad is calculated according to these distances. Consequently, the quality of assembling the camera module is enhanced.