To provide a means for protecting a battery-driven luminous body which is detachably attached to an upper-end opening of a tubular road sign with an opened upper end, formed in an approximate long-circular-truncated-cone shape in a side view from stain and damage.

This cover member is engaged with the upper-end opening of the tubular road sign with the opened upper end formed in the approximate long-circular-truncated-cone shape in a side view. The cover member comprises an outer tube with a top wall which is externally fitted to the upper end of the tubular road sign, and an inner tube which is suspended through the outer tube from the top wall of the outer tube, has a notch for locking a protrusion of the battery-driven luminous body, and is formed integrally with the outer tube.