A method for producing an integrally bladed rotor, the integrally bladed rotor comprising a rotor disc and a three-dimensional and planar blade that is integral to the rotor disc and that has a positive-pressure surface and a negative-pressure surface as main surfaces, the method comprising: rough machining the integrally bladed rotor and the blade of the integrally bladed rotor into a wing shape; obtaining a three-dimensional model of the blade of the integrally bladed rotor to be produced; on the three-dimensional model: dividing a ridge of a front edge of the blade and a ridge of a rear edge of the blade into a predetermined number of ridge pieces, setting imaginary lattice points on the respective ridge pieces, and setting a closed curve around the blade such that the closed curve passes through: a front-edge imaginary lattice point that is among the imaginary lattice points set on the front edge and that has an arrangement order as counted from the rotor disc; a rear-edge imaginary lattice point that is among the imaginary lattice points set on the rear edge and that has the same arrangement order as counted from the rotor disc; the positive-pressure surface; and the negative-pressure surface; the method further comprising: preparing a machining command for forming the closed curve continuously in a spiral shape and causing a cutting edge of a turning tool to interpolate the closed curve by moving along the spiral shape; and based on the machining command, cutting the blade by circumferentially moving a cutting point around the blade, the cutting point corresponding to a position of the cutting edge. rough machining the integrally bladed rotor and the blade of the integrally bladed rotor into a wing shape; obtaining a three-dimensional model of the blade of the integrally bladed rotor to be produced; on the three-dimensional model: dividing a ridge of a front edge of the blade and a ridge of a rear edge of the blade into a predetermined number of ridge pieces, setting imaginary lattice points on the respective ridge pieces, and setting a closed curve around the blade such that the closed curve passes through: a front-edge imaginary lattice point that is among the imaginary lattice points set on the front edge and that has an arrangement order as counted from the rotor disc; a rear-edge imaginary lattice point that is among the imaginary lattice points set on the rear edge and that has the same arrangement order as counted from the rotor disc; the positive-pressure surface; and the negative-pressure surface; dividing a ridge of a front edge of the blade and a ridge of a rear edge of the blade into a predetermined number of ridge pieces, setting imaginary lattice points on the respective ridge pieces, and setting a closed curve around the blade such that the closed curve passes through: a front-edge imaginary lattice point that is among the imaginary lattice points set on the front edge and that has an arrangement order as counted from the rotor disc; a rear-edge imaginary lattice point that is among the imaginary lattice points set on the rear edge and that has the same arrangement order as counted from the rotor disc; the positive-pressure surface; and the negative-pressure surface; the method further comprising: preparing a machining command for forming the closed curve continuously in a spiral shape and causing a cutting edge of a turning tool to interpolate the closed curve by moving along the spiral shape; and based on the machining command, cutting the blade by circumferentially moving a cutting point around the blade, the cutting point corresponding to a position of the cutting edge. preparing a machining command for forming the closed curve continuously in a spiral shape and causing a cutting edge of a turning tool to interpolate the closed curve by moving along the spiral shape; and based on the machining command, cutting the blade by circumferentially moving a cutting point around the blade, the cutting point corresponding to a position of the cutting edge.