A cooling device for an electric motor includes at least one closed capillary tube, within which a cooling fluid is located and which is introduced into an opening of a lamination stack of the electric motor such that the capillary tube is connected to the lamination stack to conduct heat and partially projects out of the lamination stack, such that the capillary tube has a cold end disposed outside and a hot end disposed inside the lamination stack. The cooling fluid and the degree of filling of the capillary tube with the cooling fluid is chosen such that an input of heat from the lamination stack into the capillary tube leads to evaporation of the cooling fluid, and the cold end of the capillary tube is cooled such that vapour produced during the evaporation condenses and heat input into the capillary tube is dissipated out of the capillary tube.