In a cooling device using an ebullient cooling system, the cooling performance adversely decreases if the evaporator includes projections activating the convection heat transfer and the bubble nuclei are formed on the inner wall surface, therefore, a cooling device according to an exemplary aspect of the invention includes an evaporator storing a refrigerant; a condenser condensing and liquefying a vapor-state refrigerant vaporized in the evaporator and radiating heat; and a connection connecting the evaporator and the condenser; wherein the evaporator includes a base thermally contacting with an object to be cooled, and a container; the base includes a plurality of projections on a boiling surface of a surface at an inner wall side contacting with the refrigerant; and a bubble nucleus forming surface is included only on a part of a refrigerant contacting surface including the boiling surface and the surface of the projections.