Transmission having a reverse shift device, comprising a counter shaft and an output shaft supported rotatably and in parallel with each other within a transmission casing, a plurality of speed change gear pairs and a reverse gear train for performing power transmission between the counter shaft and the output shaft, and a shift mechanism for performing selective changeover of power transmission between the counter shaft and the output shaft through the speed change gear pairs and the reverse gear train, the reverse gear train comprising a driving gear and a driven gear provided on the counter shaft and the output shaft and rotating with the counter shaft and the output shaft, respectively, and an idle gear supported in such a manner as to be rotatable and movable in an axial direction by a support shaft provided on the transmission casing in parallel with the counter shaft and the output shaft, the shift mechanism comprising a reverse arm whose proximal end portion is supported on the transmission casing in such a manner as to be pivotable about an axis orthogonal to the support shaft, whose distal end portion is slidably inserted into an annular groove formed in an outer circumference of the idle gear, and which has a driven hole formed in an intermediate portion thereof, elongated in a direction connecting the proximal end portion and the distal end portion, and extending through the intermediate portion in a direction parallel to the axis orthogonal to the support shaft, and a reverse fork supported on the transmission casing in such a manner as to be movable in parallel with the support shaft and having a driving pin engaged with the driven hole, and the idle gear being moved in an axial direction of the support shaft between an engagement position where the idle gear is engaged with the driving and driven gears, and a disengagement position where the idle gear is disengaged from the driving and driven gears, by means of moving the reverse fork in the axial direction and thereby pivoting the reverse arm, characterized in that the reverse shift device has a jump-over mechanism is provided between the reverse arm and the transmission casing and elastically urges the reverse arm outward away from a predetermined intermediate position within a pivoting range of the reverse arm, an outside diameter of the driving pin (51 c) of the reverse fork is smaller than a width between opposed flat inner side surfaces of a longitudinally intermediate portion of the driven hole of the reverse arm so as to form a gap between the driving pin (51 c) and the inner side surfaces of the driven hole, and when the reverse arm is situated on a side of the predetermined intermediate position such that the distal end portion thereof is engaged with the idle gear situated at the disengagement position, the driving pin (51 c) is elastically in contact with one of the opposed flat inner side surfaces of the longitudinally intermediate portion of the driven hole, and, when the reverse arm is situated on the other side of the predetermined intermediate position such that the distal end portion thereof is engaged with the idle gear situated at the engagement position, the driving pin (51 c) is elastically in contact with the other one of the opposed flat inner side surfaces of the longitudinally intermediate portion of the driven hole.