The present invention relates to a transmission apparatus of an agricultural working automobile, the transmission apparatus comprising: a first gear-shifting part for performing gear-shifting to adjust the speed of an agricultural working automobile； and a second gear-shifting part for performing gear-shifting to adjust the speed of the agricultural working automobile, wherein the second gear-shifting part comprises a sub-gear-shifting drive mechanism for performing gear-shifting, using one operation selected from among an operation transferred through a first power transmission path from the first gear-shifting part and an operation transferred through a second power transmission path from the first gear-shifting part
