PROBLEM TO BE SOLVED: To provide a shift mechanism of transmission which is excellent in shift feeling of a driver, is inexpensive and has a single rail structure.SOLUTION: The shift mechanism includes: a select shaft SA which turns in response to a select operation of a shift lever; a fork shaft SB which moves in the shaft direction in response to a shift operation of the shift lever; and forks F1-F3 arranged on the fork shaft SB relatively movably in the shaft direction, respectively independently of each other. One fork corresponding to a shift transmission stage selected by the select operation of the shift lever among the forks F1-F3 is integrally connected to the fork shaft SB and moves in the shaft direction integrally with the fork shaft SB in response to the shift operation of the shift lever. Meanwhile, the remaining forks are not connected to the fork shaft SB, are connected integrally with the select shaft SA and are fixed in the shaft direction.