The invention discloses a radially-adjustable heavy-duty cutting layer milling cutter applicable to the field of heavy-type milling processing, and aims to solve the problems that during heavy-duty milling water chamber end enclosing, surfaces of workblanks are uneven, multi-defective and poor in machinability; cutting blades are prone to being damaged by impacts during rough machining or hogging machining; during milling, cutting depth changes frequently, which results in that not all cutter teeth are involved in cutting, utilization rate of the milling cutter is low, the cutting layer milling cutter of a fixed radial stepped structure is short in service life, machining efficiency is influenced and the like. Cutter teeth of the cutting layer milling cutter are designed in a stepped distribution, by means of increasing cutting depth, metal removal rate is increased, and machining efficiency is improved; by the aid of a radial adjusting mechanism, the cutting blades in an upper layer are enabled to move radially, a proper overhang amount can be selected, and strength of the cutting blades is enhanced. A radially-adjustable cutter pad is positioned by a pad block, auxiliary time including cutter amounting time, cutter adjusting time and the like is saved; up-warp chip holding grooves are formed in a cutter body in design, the depths of the positions, close to the cutting blades, of the chip holding grooves are far larger than that of the positions, distant from the cutting blades, of the chip holding grooves, up-warp slopes are formed in the chip holding grooves, and when cutting chips flow in the chip holding grooves, the chips can be separated from the cutter body quickly, friction between the chips and the cutter body is reduced, and service life of the cutter body is prolonged.