A traction drive tool adapter, has a rotary portion provided at its front half section with planetary roller-inserting bores extending radially from the outer circumferential surface of the rotary portion into a central bore therein, each of the roller-inserting bores having planetary rollers driving shaft member-setting grooves continuing from two ends of the roller-inserting bore that are opposed to each other in the axial direction of the central bore. Each driving shaft member which supports a relative planetary roller is set in the front half section of the rotary portion by inserting the planetary roller from the side of the outer circumferential surface of the front half section in the radial direction of the rotary portion into the roller-inserting bore, and the end sections of the shaft member into the shaft member-setting grooves, and the outer circumferential section of each planetary roll is engaged with an annular fixed track in a fixed portion of the adapter and the outer circumferential section of a sun roller in a tool mount portion of the adapter. A thread is provided in a through bore extending from the rear end of the rotary portion to the central bore in the axial direction thereof, and a male screw is engaged with the thread. Labyrinth seals are provided at the outer ends of the relative rotary regions between the fixed, rotary and tool must portions, and elastic contact lip-carrying rings are fitted on the inner side of the labyrinth seals.