A warning structure includes a bracket and a warning member mounted on the bracket. The bracket includes a main body, rollers rotationally mounted to the main body, and a stopping assembly including a rotating mechanism and a stopping member coupled to the rotating mechanism. The rotating mechanism is rotationally coupled to the main body. One of the rollers is mounted adjacent to the stopping member. When the rotating mechanism is rotated, the stopping member is engaged with a ground to prevent the bracket from moving.