Abstract: A skateboard includes a step board and two wheel assemblies spacedly mounted underneath the step board, wherein each of the wheel assemblies includes two wheels and a truck unit. The truck unit includes a truck having two side ends rotatably mount the two wheels respectively, a washer pad mounted between the step board and the truck, and a safety alert system which includes a power source supported underneath the step board and at least an illuminator electrically connected to the power source, wherein the illuminator is positioned at an exterior of the truck to provide a light effect for enhancing a visibility of the skateboard so as to prevent unwanted accidents and improve safety.