The door handle contains a positioning element, an engaging ring, and a handle member. The positioning element is flat and substantially rectangular with four rounded corners. Four notches are formed besides the four corners, respectively. The inner circumference of the engaging ring is divided equally into four arc sections, each having a J-shaped track. Along the outer circumference of the engaging ring, a curved slot where an elastic plate is embedded and a neighboring axial groove are provided. After the positioning element is fixed to a lock on a door, the engaging ring and a first cover of the handle member are sleeved over the positioning element. By twisting the first cover which in turn rotates the engaging ring, the four corners follow the J-shaped tracks and are thus locked and the elastic plate is embedded into one of the notches.