To provide a work device capable of easily obtaining a soft worked surface of waveform or the like.

This device comprises a tool chuck 4b mounting a work tool 4, output rotary shaft 3 mounting this tool chuck 4b in one end, and a rocking rotation converting mechanism 2 (for instance, output rotary shaft 3 is in eccentric position of rotary plate 22, that is, shaft mounted rotatable in position slightly deviated from center point) auto rotating the output rotary shaft 3 by rotation of a drive rotary shaft also revolving the output rotary shaft 3 on a circular track with the drive rotary shaft serving as the center. The rocking rotation converting mechanism is fixed to an end part of the drive rotary shaft also provided with a rotary plate 22, planet gear shaft 27, drive planet gear 25, output planet gear 26, drive gear auto rotating gear 25a, and an output gear 28.