To provide an industrial robot having a structure in which a total reduction ratio of a joint mechanism can be easily modified without changing a reduction gear, in an industrial robot including a joint mechanism of a swivel base or an arm which has, as a driving source thereof, a servomotor provided with a position sensor and driven by a servo mechanism via the reduction gear.

A joint mechanism is configured of a reduction gear 11 anchored to a base 1 and rotatable with respect to the base 1 about an axis 3 of a swivel base 2, a servomoter 12, and a gear box case 16 disposed between the servomotor 12 and the reduction gear 11. The gear box case 16 houses an idle gear 14 which engages with a pinion gear 15 connected to a shaft 11 of the servomotor 12 and an input gear 13 for the reduction gear 11 which engages with the idle gear 14. For the idle gear 14, the gear box case 16 is provided with a plurality of idle gear mounting holes 21 and 22 corresponding to the number of teeth of the replaceable pinion gears 15 and 20.