To provide a partially untoothed gear hardly broken and configured such that even though the tooth tip of a first tooth abuts on the tooth tip of a driving gear, the tooth tip of a second tooth does not abut on the tooth tip of the driving tooth.

This partially untoothed gear is formed from elastic materials and has a tooth part 30 and a missing part 21. The first tooth 31 and second tooth 32 of the tooth part 30 in the rotational direction of the gear are separated from each other, a flexible part 23 is formed by providing a slit 22 directed to an upstream side in the rotational direction of the gear, and the missing part 21 is formed on the peripheral part of the flexible part 23. The first tooth 31 only is provided on the end portion of the flexible part 23, and the second tooth 32 and the subsequent teeth are provided on a main portion 24 of the gear.