To reduce the axial length L of a transmission.

The transmission is configured such that a pair of first stage gears 26a, 26b are provided between a first stage input shaft 14 and a first stage output shaft 20, and a pair of fourth stage gears 30a, 30b are provided between a second stage input shaft 18 and the first stage output shaft 20, respectively. A pair of third stage gears 34a, 34b and a pair of fifth stage gears 36a, 36b are provided between the first stage input shaft 14 and a second stage output shaft 22, and a pair of second stage gears 40a, 40b and a pair of sixth stage gears 30a, 42b are provided between the second stage input shaft 18 and the second stage output shaft 22, respectively. A reverse stage input gear 34a integrated with the first stage input shaft 14 is coupled to a reverse stage output gear 46b provided on the first stage output shaft 20 via idle gears 46c, 46d arranged on a counter shaft 24.