The invention concerns a device for regulating the relative angular speed between a magnetic structure and a resonator magnetically coupled to each other and forming an oscillator which defines a magnetic escapement. The magnetic structure includes at least one annular magnetic path at least partially formed of a magnetic material of which one physical parameter is correlated to the magnetic potential energy of the oscillator, the magnetic material being arranged along the annular path so that the physical parameter varies angularly in a periodic manner. The annular path includes, in each angular period, an area of accumulation of magnetic potential energy in the oscillator, radially adjacent to an impulse area. The magnetic material, in each accumulation area, is arranged so that the physical parameter of said magnetic material gradually increases angularly or gradually decreases angularly.