When it is confirmed that a distal end portion of an attachment has reached a predetermined distance detection start position apart from a cab on the basis of a posture of the attachment detected by posture detector, a control apparatus determines whether or not an object to be detected has reached a predetermined stop position closer to the cab than the distance detection start position on the basis of a distance of the object to be detected by a distance detection sensor, and controls the drive unit so as to stop the attachment when determining that the object to be detected has reached the stop position, and the control apparatus controls the drive unit so that the speed of the distal end portion of the attachment becomes a predetermined target speed or lower when the distal end portion of the attachment reaches the distance detection start position.