A light-producing warning device for skateboard includes a case connected to an underside of a deck of the skateboard for accommodating batteries; a control circuit unit mounted in the case to electrically connect to the batteries and including a switch; a cover closing the case and having a push button provided thereat corresponding to the switch on the control circuit unit; at least one light-emitting element attached to an outer periphery of the deck and connected to wires extended from the switch; and at least one light-transferring strip connected to the light-emitting element and fixed to the outer periphery of the deck with fixing nails and having a plurality of through holes spaced thereon. By pushing the push button to touch the switch, light is emitted by the light-emitting element to pass through the light-transferring strip and form light spots on the spaced through holes to provide good warning effect.