A ball bearing cage having a first ring element and a second ring element is provided. The ring elements are each formed from sheet metal, and each include axial bulges separated by support surfaces. Ball guide pockets are formed between facing bulging inner walls by joining the support surfaces of the two ring elements. The ring elements are formed in such a way that the bulging inner walls that define the ball guide pockets define a channel cross-section which is concave in relation to a ball and which has an inner and an outer ball contact zone. The channel cross-section has such a depth in a groove base lying between said inner and outer ball contact zones that, when the ball comes into contact with the ball contact zones, an intermediate space remains between the ball and the groove base lying between the ball contact zones.