A traveling transmission device for a tractor, comprising: a front wheel differential mechanism for transmitting power to left and right front wheels; a rear wheel differential mechanism for transmitting power to left and right rear wheels; and a transmission to input power from a power source and to transmit the inputted power to the front wheel differential mechanism and the rear wheel differential mechanism; wherein the transmission includes: a front wheel transmission shaft for transmitting power to the front wheel differential mechanism; a front wheel clutch that can be switched over between an engaged state for transmitting power to the front wheel transmission shaft in such a manner that an average circumferential speed of the left and right front wheels is set equal to an average circumferential speed of the left and right rear wheels and a disengaged state for disconnecting power transmission to the front wheel transmission shaft; and a front wheel acceleration clutch that can be switched over between an engaged state for transmitting power to the front wheel transmission shaft in such a manner that the average circumferential speed of the left and right front wheels is set higher than the average circumferential speed of the left and right rear wheels and a disengaged state for disconnecting power transmission to the front wheel transmission shaft, and the front wheel clutch and the front wheel acceleration clutch are supported to the front wheel transmission shaft side by side in an axial direction of the front wheel transmission shaft, characterized in that: between the front wheel clutch and the front wheel acceleration clutch, there is provided a holder rotatably supporting the front wheel transmission shaft; a first operational oil passage configured to switch over the front wheel clutch between the engaged state and the disengaged state by supplying and discharging of pressure oil is formed respectively in and between the front wheel transmission shaft and the holder; and a second operational oil passage configured to switch over the front wheel acceleration clutch between the engaged state and the disengaged state by supplying and discharging of pressure oil is formed respectively in and between the front wheel transmission shaft and the holder. a front wheel differential mechanism for transmitting power to left and right front wheels; a rear wheel differential mechanism for transmitting power to left and right rear wheels; and a transmission to input power from a power source and to transmit the inputted power to the front wheel differential mechanism and the rear wheel differential mechanism; wherein the transmission includes: a front wheel transmission shaft for transmitting power to the front wheel differential mechanism; a front wheel clutch that can be switched over between an engaged state for transmitting power to the front wheel transmission shaft in such a manner that an average circumferential speed of the left and right front wheels is set equal to an average circumferential speed of the left and right rear wheels and a disengaged state for disconnecting power transmission to the front wheel transmission shaft; and a front wheel acceleration clutch that can be switched over between an engaged state for transmitting power to the front wheel transmission shaft in such a manner that the average circumferential speed of the left and right front wheels is set higher than the average circumferential speed of the left and right rear wheels and a disengaged state for disconnecting power transmission to the front wheel transmission shaft, and the front wheel clutch and the front wheel acceleration clutch are supported to the front wheel transmission shaft side by side in an axial direction of the front wheel transmission shaft, characterized in that: between the front wheel clutch and the front wheel acceleration clutch, there is provided a holder rotatably supporting the front wheel transmission shaft; a first operational oil passage configured to switch over the front wheel clutch between the engaged state and the disengaged state by supplying and discharging of pressure oil is formed respectively in and between the front wheel transmission shaft and the holder; and a second operational oil passage configured to switch over the front wheel acceleration clutch between the engaged state and the disengaged state by supplying and discharging of pressure oil is formed respectively in and between the front wheel transmission shaft and the holder. between the front wheel clutch and the front wheel acceleration clutch, there is provided a holder rotatably supporting the front wheel transmission shaft; a first operational oil passage configured to switch over the front wheel clutch between the engaged state and the disengaged state by supplying and discharging of pressure oil is formed respectively in and between the front wheel transmission shaft and the holder; and a second operational oil passage configured to switch over the front wheel acceleration clutch between the engaged state and the disengaged state by supplying and discharging of pressure oil is formed respectively in and between the front wheel transmission shaft and the holder.