To enhance the tamping efficiency by providing tool blades adjoining in a longitudinal direction of the machine of two multiple tamping units in a manner spaced at a mutual distance equal to the distance of crossties.
After the machine unit 1 is traveled and stopped at the operation site, two multiple tamping units 18, 19 are moved downward simultaneously by the elevation driving means 25 of a main tamping machine 4. Each tamping tool 21 of the multiple tamping units 18, 19 is vibrated by a vibration device 23. Then, a pair of tool blades 20 mutually spaced at the crosstie distance (a) of the tamping tool 21 is allowed to operate respective collection movements by a squeeze driving device 24 for simultaneously tamping the ground under a pair of crossties 22. In addition, after the multiple tamping units 18, 19 are moved upward, the are moved five times as long as the crosstie distance (a) together with a working frame 14 by means of a shift driving device 66, and a tamping operation is performed again.