The invention relates to a traveling mower including a traveling body 1 with a mower unit, and a grass collection box 22 for storing the mowed grass. The box is pivotally connected to the traveling body for switching between a grass collection posture for receiving grass and a discharge posture for discharging grass. The body 1 is provided with a posture change lever 12. The box 22 and the lever 12 are associated with each other via an interlock mechanism 44 so that the box 22 changes the posture in accordance with the manual operation of the lever 12. The change of the posture of the box 22 is performed with a small operation force that depends on the amount of the grass in the box 22. To enable this, the interlock mechanism 44 includes a switching mechanism for increasing the turning angle of the box 22, per unit operation of the lever 12, when the box 22 is empty or substantially empty and for reducing the turning angle when the box 22 holds much grass.
