A ripper assembly is arranged in that one end of an arm is pivotally attached to a vehicle body while a beam comprised with shanks is pivotally attached to the other end of the arm, and in that a tilt cylinder and a lift cylinder are respectively interposed between the vehicle body and the beam at a position upward of the arm. One end side of the lift cylinder is pivotally attached, on a vehicle body side, at a position upward of a vehicle body-sided pivotally supporting portion of the tilt cylinder. The other end side of the lift cylinder is pivotally attached, on a beam side, at a position downward of a beam-sided pivotally supporting portion of the tilt cylinder.