PURPOSE: To simplify construction of a mechanism and facilitate also its work, by providing two leaf springs, acting in directions crossing at right angles, and reaction force detecting mechanisms between a table and a block and the block and a base, in the case of the force sensing tool holding mechanism used for cast finishing work or the like.

CONSTITUTION: A supporting mechanism respectively supports a table 1 to both end surfaces 15a, 15b of a block 15 by the first leaf spring 16 flexing in a tool pressing direction Z and the block 15 to a base 10 by the second leaf spring 17 flexing in a direction X. And the mechanism provides a reaction force detecting mechanism 18, by a magnet 7 and a differential type magnetic resistance element 8, between the table 1 and the block 15 while the second reaction force detecting mechanism 19 similarly between the block 15 and the base 10. A tool supporting mechanism 20 as in the above, being supported by a robot 21, performs work by holding a tool 23 through a connecting member 24. The table 1, receiving reaction force in the direction X by grinding work, obtains an output potential by the reaction force detecting mechanism 19. Force is obtained by the output potential by previously obtaining said output potential and a characteristic of the force.