Disclosed are an apparatus and method of filtering a narrow band X-ray. The apparatus includes a micro filter array to configure a plurality of micro filters in an array, a filter array storing unit to store a filter table having information about an angle of each of the plurality of micro filters within the micro filter array, and a control unit to retrieve the filter table to ascertain the angle of each of the plurality of micro filters. The control unit also controls an angle between each of the plurality of micro filters and a panel supporting the plurality of micro filters to be the ascertained angle, and filters and output a received broadband polychromatic X-ray to be the narrow band X-ray.