An automatic slowdown control apparatus for a vehicle is disclosed wherein automatic slowdown control can be ended appropriately and automatic slowdown is prevented from being performed excessively on a road of an ascending gradient. The automatic slowdown control apparatus starts automatic slowdown control of rendering a braking mechanism operative to slow down the vehicle when the stability of the posture and/or behavior of the vehicle upon turning is deteriorated. A control end threshold value is set such that the stability of the vehicle is displaced to the instability side as the ascending gradient of the uphill road increases.