Abstract: A method comprising interpenetrating a hollow casing into a relatively loose sand layer saturated with ground water, thereafter raising the casing while tamping crushed stones charged into the casing by a compaction rod disposed within the casing, and driving gravel drain piles while continuously performing the raising of the casing and the tamping of the crushed stones. After the casing has reached the predetermined depth and the charging of crushed stones has been confirmed an, amplitude of reaction is detected by a reaction detection device provided on the compaction rod or a load current measuring device of the compaction rod. The reaction value is compared with a set reaction value, and one or more factors (a raising speed of the casing, a period, an amplitude and an extreme end surface-height of the compaction rod for determining a compacting degree of a peripheral ground) are controlled in response to the compared value.