Disclosed are an apparatus for detecting pipe wall thinning, which measures a natural frequency of a pipe and determines a level of the pipe wall thinning, and a method thereof.The apparatus for detecting the pipe wall thinning includes a hitting member 10 for hitting the pipe T, a vibration measurement sensor 20 which measures a vibration signal generated when the pipe T is hit with the hitting member 10, and a control part 30 which compares the natural frequency calculated from the vibration signal measured from the vibration measurement sensor 20 with a natural frequency generated from a normal pipe in which wall thinning does not occur, and determines the level of the wall thinning of the pipe T.