Abstract: An illuminating warning device has a transparent casing, a cap and an inner tube. The casing is provided to receive therein the inner tube that has a plurality of circuits boards securely mounted on the outer periphery thereof and having a plurality of illuminating elements electrically connected with the circuit boards. A switch mounted on the inner tube and protruded out from the periphery of the casing is able to control the illumination of the illuminating elements in the casing. Furthermore, a magnet received in the bottom of the inner tube enables the device to magnetically adhere to a metal surface as a warning signal to others.