The present invention provides cutter discs for milling an inner retaining surface and capable of rotating. According to the cutter discs, a plurality of guide grooves are uniformly arranged on the outer circles of the left cutter disc and the right cutter disc, the force surfaces of each guide groove are provided with cutting blades, wedge pressing blocks are arranged in the guide grooves, the inclined surface of the wedge pressing block contacts the cutting blade, the cutting blade is fixed in the guide groove through a screw, an adjusting screw is arranged on the back surface of the force surface of each cutting blade, the installation surfaces of the left cutter disc and the right cutter disc are provided with inner counterbores, and wedge thread adjusting blocks are correspondingly arranged in the inner counterbores. According to the present invention, the total thickness can be controlled within the retaining opening range of the part, the cutting blade can be fixed in the guide groove through the effect of the wedge pressing block, the movable installation of the cutting blade has characteristics of convenient use, welding cost saving, no cutter disc deformation caused by welding, and use stability and reliability ensuring, the processing on the work-piece with the inner retaining surface size of 40-45 mm is well solved, the operation is convenient, and the structure is practical.