Provided are a travel assist device capable of producing, in a preferred manner, warning vibrations notifying deviation of a vehicle with respect to a travel path, and a method of controlling the same. A travel assist device includes a travel assist control device that notifies a driver about an anti-deviation direction or a deviation direction by making a steering angular acceleration in the deviation direction and the steering angular acceleration in the anti-deviation direction different from each other when producing warning vibrations, wherein a time-derivative value of a steering angle of a steering wheel is defined as a steering angular velocity, and a time-derivative value of the steering angular velocity is defined as the steering angular acceleration.