Abstract: A method of controlling a synchromesh type automatic transmission of a vehicle such as an automobile, including the steps of releasing a clutch for connecting an engine and the transmission in response to a speed change command, shifting the transmission from one speed position to a neutral position, shifting the transmission from the neutral position to a subsequent speed position, and applying the clutch. The double-clutching operation is conducted if a load upon synchronization during the speed changing operation exceeds a predetermined level, to once apply the clutch and subsequently release the clutch again while the transmission is in the neutral position. Thus, the synchronization load can be dropped to prevent any so-called "under-synchronization" in the transmission. The synchronization load is detected in terms of the difference between the r.p.m. of the input shaft of the transmission and the product of the vehicle speed or the r.p.m. of the output shaft of the transmission and the reduction ratio.