(57) The known separator for use in pulverizer of the type that a plurality of blades (1) are disposed about a substantially vertical center axis of rotation as sepa­rated by a predetermined radius therefrom and as directed in the vertical direction, is improved so that a cross-­section area of passage of airflow between blades can be taken broad and yet it may not be varied even under influence of a centrifugal force. The improvements reside in that the blade (1) is made of a flat plate rather than a shaped material, and that the separator is provided with an annular body (2) for connecting the blades so as to sur­round the center axis of rotation. A tension to be generated in the annular body (2) as a result of a centrifugal force and a reinforcement effect of the annular body (2) are mathematically analyzed as a basis of design of the improved rotary separator.