to the inside of the coil assembly 40 and an outer flow path to the outside of the coil assembly 40 selectively as an exemplary embodiment of the present invention as illustrated in fig8 two or more flow path separators may be installed in the inner flow path or the outer flow path in this case an upper passage and a lower passage may be additionally formed depending on the number of the flow path separators that is in order for the mr fluid to circulate for only half a turn along the perimeter of the coil assembly a first flow path separator 60 a and a second flow path separator 70 a are additionally installed on the opposite side and in order for the mr fluid which has been blocked from flowing by means of the additionally installed flow passage separators 60 a and 70 a to be discharged outward lower passages 12 c and 12 d and upper passages 52 c and 52 d may be additionally installed in the lower plate 10 and the upper plate 50 partitions of such flow paths may be formed according to the properties of mr fluid such as viscosity particle density.