A gear transmission having a speed changing section includes a speed changing gear for setting a speed stage and a shift gear slidably mounted on a rotation support shaft and operated to engage and disengage with the speed changing gear, the speed changing section configured to speed-change inputted power and to output the resultant power via the rotation support shaft. An arrangement is provided for facilitating engagement of the shift gear with the speed changing gear even when respective end faces of the shift gear and the speed changing gear hit each other. A transmission mechanism (20B) is provided for outputting power of a rotation support shaft (24) to a traveling device. The transmission mechanism (20B) has a transmission flexibility portion (80) which allows free rotation of the rotation support shaft (24) by a set rotation angle.