In a twin clutch transmission, a first main shaft transfers rotation power of a crankshaft that is provided in parallel, input via a first clutch, to a drive shaft via an odd-numbered transmission gear mechanism. A second main shaft transfers rotation power of the crankshaft that is provided in parallel, input via a second clutch, to the drive shaft via an even-numbered transmission gear mechanism. In a first power transfer path running from the crankshaft to the drive shaft via the first clutch and a second power transfer path running from the crankshaft to the drive shaft via the second clutch, back torque limiters are provided that, when reverse torque operates in a direction opposite the direction for acceleration of a rear wheel, limits transfer of the reverse torque.