A focusing adjustment method of a camera module predicts, before completion of securing of a camera board to an optical system, a shrinkage deviation amount by which the optical system and the camera board will approach one another. The focusing adjustment method adjusts a position and an angle of the camera board to separate, by the predicted shrinkage deviation amount, the camera board from the optical system as compared with a focusing attitude of the image sensor with respect to the optical system where the optical system is in focus on the image sensor to accordingly offset the predicted shrinkage deviation amount.