To obtain a harmonic gear using a permanent magnet which can obtain a high reduction gear ratio and which can stably and freely elliptically deform a flake spline for a long period of time even when the magnet having a hard rigidity and high energy product is used.

A magnet ring 3 is constituted by aligning bar-like magnet pieces 3a in the circumferential direction of the same pole contained in a resin 3b having flexible elasticity, and is mounted inside the opening side of the flame spline 2. A rotor 4 in which the permanent magnet opposite to the piece 3a is disposed so that the ring 3 is elliptically deflected by the magnetic force of the ring 3 is provided inside the ring 3. This rotor 4 is rotated by elliptically deflecting the spline 2 via the ring 3 and engaging a part of outer teeth of the spline 2 with inner teeth of a fixed circular spline 1, of which the number is slightly larger than that of the out a piece, at same pitches, the deflection is rotated, thereby obtaining reduced rotation from the flame spring 2.