PURPOSE: To form a correct roadbed by allowing various adjustments for each four tamping unit connected to a connection drive device and vibration drive device, for high tamping efficiency in line or point section.

CONSTITUTION: Four tamping tools 6, 7, 8, and 9 of four taming units 3 are connected to two ballast tamping machine heads 16 arranged side by side in the direction orthogonal to longitudinal direction of the machine. A block device 19 for selectively connecting to each of outside frames 14, in the lateral direction of the machine, to an adjacent inside frame 14 is provided. When a point section comprising a main line/branch line 21 or 22 is completed with a connection drive device 4 and vibration drive device 5, two inside/outside tamping units 3 arranged side by side for tamping each of rail sections are re-connected to a common tamping unit while forming one structural unit with the assistance of the block device 19.