Abstract: An improved multi-purpose drilling machine of the type including a self-propelled vehicle to which is fitted a fifth wheel (5) that carries a support and movement unit (2) for a drilling-rod boom (4). The machine includes a system of counterweights (6) mounted on the fifth wheel (5) on the opposite side of the drilling-rod boom to the axis of rotation of the fifth wheel. The counterweights are designed to offset, at least partly, the moment created by the drilling-rod boom on the structure of the machine. In particular, the drilling-rod boom (4) is mounted at the end of an upright (3), which in turn is hinged to the fifth wheel (5) so that the boom (4) can be moved from a substantially vertical to a substantially horizontal position and vice versa, the fifth wheel (5) rotating around an axis parallel to the longitudinal axis of the machine.