A control device of a vehicle has a hill ascent angle update determiner, a slope estimator, a deceleration determiner, and a hill ascent angle estimator. The deceleration determiner determines that a vehicle is in a deceleration state when the throttle opening is equal to or lower than a threshold. The hill ascent angle update determiner prohibits update processing of an estimated hill ascent angle in the increase direction by the hill ascent angle estimator if the slope estimator estimates that a road surface has an upward slope and the deceleration determiner determines that the vehicle is in the deceleration state.