The invention is intended to make it possible to reduce the overall lengths of a vertical shaft and a fore/aft shaft, while securing sufficient shaft strengths thereof, so that the vertical dimension from the fore/aft shaft to a tilt cylinder may be formed short and to render the construction on the rear face side of a blade compact. A traveling machine body 2 pivotally supports a dozer frame 3 via a horizontal shaft, the dozer frame 3 being lifted up/down via a dozer cylinder S1. This dozer frame 3 pivotally supports, via a vertical shaft Y, a support body 4 which is pivoted back and forth via an angle cylinder S2, and this support body 4 pivotally supports, via a fore/aft shaft Z, a blade 5 which is vertically pivoted via a tilt cylinder S3. The support body 4 supports the fore/aft shaft Z downwardly and forwardly of the vertical shaft Y, and the tilt cylinder S3 is disposed upwardly and forwardly of the vertical shaft Y and upwardly of the fore/aft shaft Z.