Drive connecting shaft structure for rotating tool

With respect to a connection structure of a connecting shaft for transmitting a rotary drive force to a rotating tool via a rotating tool holder, an objective of the present invention is to provide a floating mechanism that is capable of compensating for misalignment between the rotating tool holder and the shaft center of the connecting shaft. This structure of a connecting shaft for transmitting a drive force to a rotating tool holder is characterized in that the connecting shaft has a coupling section for the rotating tool holder, and a connection body section for connecting to a rotary drive unit, is a fitting structure in which a mounting projecting section provided on one of the coupling section or the connection body section is fitted with a mounting recessed section provided in the other, and constitutes a floating structure that compensates for misalignment in the radial direction of the shaft center between the mounting projecting section of the one and the mounting recessed section of the other.