An automatic transmission control device with which it is occurrence of meshing failure at the time of engaging an engagement clutch may be prevented while suppressing prolonged time for completing the engagement. Disclosed is an automatic transmission control device comprising: an automatic transmission that is provided in the drive system of a vehicle and that includes, as an coupling element, an engagement clutch which undergoes meshing/engagement at the time of coupling; and a transmission controller that performs transmission control of the automatic transmission. The engagement clutch includes: a clutch gear connected to a transmission input shaft; and a clutch hub connected to a transmission output shaft and capable of meshing with the clutch gear. At the time of shifting at which the engagement clutch is engaged, the transmission controller sets a target differential rotation speed for generating a predetermined differential rotation between the input rotation speed and the output rotation speed in the engagement clutch when the clutch gear and the clutch hub mesh with each other.