To provide a braking device for traveling of a work machine capable of constituting the capacity of braking system for traveling small and hopefully capable of reducing a space required for an operation system by improving a transmission system for a rice planting machine.

This braking device for traveling of the rice planting machine is provided with a hydrostatic continuously variable transmission device 8 changing speed of engine power, a front missions 10 to which the output thereof is inputted, and a rear mission receiving the power from the front mission 10 and transmitting the power to right-and-left rear wheels. The front mission 10 is equipped with a brake-mechanism 32A with a wet friction structure capable of freely and forcibly stop the rotation of a first shaft 81 to which output rotation of the hydrostatic continuously variable transmission device 8 is inputted.