To provide a speed reducing unit reducing rotation speed of an output shaft in relation to rotation speed of an input shaft, capable of being constructed in a very small size by eliminating a space where a suitable bearing such as artificial ruby is arranged.

This speed reducing unit 1 reduces rotation speed of the output shaft 12 in relation to rotation speed of the input shaft 11 and is provided with a plurality of gears 51 meshing each other, a plurality of shafts 61 supporting a plurality of the gears 51, and a plurality of shafts 61 supporting a plurality of the gears 51. At least one of the plates 21 is made of material having sliding nature such as powder metal material impregnated with oil, powder metal material having solid lubricant such as graphite mixed therein, or powder metal material having fiber having sliding nature mixed therein.