A roller bearing cage is disclosed in which a pair of semicircular cage halves is assembled with their mating ends thereof coming into abutment against each other. The mating ends are chamfered off to stave off bearing failure resulting from any deformation that might occur at the areas nearby the mating ends owing to large centrifugal force imposed by high-speed engines. The roller bearing cage may be completed by only joining together the semicircular cage halves with their diametral mating ends coming into engagement with one another. Each of the semicircular cage halves is composed of axially opposing semicircular rims and cage bars interposed between the rims, thus helping ensure stiffness with even weighing less. The chamfering operation is done to make even any outer peripheral areas nearby the mating ends, preparatory to cutoff operation to split a cylindrical cage stock into two halves. This helps the process management of material-removal work to make the chamfered even areas.