A lockup disengagement control device for an automatic transmission including a torque converter including a lockup clutch, and a lockup control section, the lockup disengagement control device includes: when a brake is operated from a brake OFF to a brake ON during a coast traveling in an engagement state of the lockup clutch, the lockup control section being configured to sense an initial deceleration by the brake ON operation, and to set a lockup release vehicle speed to be higher as an absolute value of the initial deceleration is greater, and when a vehicle speed is sensed to be equal to or smaller than the set lockup release vehicle speed in a middle of a brake deceleration scene by the brake ON operation, the lockup control section being configured to disengage the lockup clutch.