To overcome problems that the cost of a device is high and the cost for maintaining and managing of cooling water is high due to the necessity of an exclusive cooling source in a cooling device of an LED light source using cooling water used for a printer using ultraviolet curable type ink.

The cooling device 14 for the LED light source uses dampening water 4 of a printer as the cooling source. That is, the cooling device 14 of the LED light source includes a heat exchanging unit 8 for carrying out heat exchange between the cooling water and the cooling source, a pump unit 12 for pumping out the cooling water, an LED light source unit 11 having a flow channel of the cooling unit, and an expansion absorbing unit 15 for absorbing the volume change in the cooling water in the circulation passage of the cooling water for cooling the LED light source 11 attached to the printer. In this case, the dampening water 4 of the printer is used as the cooling source.