Abstract: Even when a bucket is changed to an optional special bucket, path control as intended by an operator can be automatically performed without making a correction of the angle of the original bucket. For this purpose, in an operation mode determining section (9), there is calculated the possibility (U2) of an operation mode being a nose-fixed mode, depending on how much a bucket attitude angle (.gamma.) deviates from a predetermined angle, and there is also calculated the possibility (U1) of the operation mode being the fixed-angle to the ground mode, depending on the magnitude of a computed value of the allowable angle held with respect to the ground, whereby the operation mode during the automatic path control can be automatically determined by comparing these possibilities (U1, U2).