A transmission 20 includes gears 421 through 426 and 441 through 446, sliders 451 through 453, an electric motor 58, a shift drum 50, shift forks 491 through 493, and a control unit 83. The sliders 451 through 453 are members different from the gears 421 through 426 and 441 through 446. The shift drum 50 includes guide grooves 61 through 63 each including a linear portion 64 and a tilt portion 65. An end of each of the shift forks 491 through 493 is located in a corresponding one of the guide grooves 61 through 63. The control unit 83 controls the electric motor 58 to rotate the shift drum 50 in such a manner that a gear-shift rotation angle is less than 60 degrees. With rotation of the shift drum 50 by the gear-shift rotation angle, the shift forks 491 through 493 move the sliders 451 through 453 in the axial direction of the shaft 21 or 22. In this manner, dog portions of the sliders 451 through 453 mesh with dog portions of the gears 441 through 446 so that rotation of the shaft 21 is transferred to the shaft 22.