Method for forming a drilled pile wall in ground, in which - several essentially vertical drill holes are drilled side by side in the ground using a drilling device, - several pipe piles for casting are installed in a row into the drill holes, - the drill hole is flushed using a medium to remove drilling waste from the drill hole, - reinforcements are installed to reinforce the pile wall structure to be formed - concrete is cast into each pipe pile installed in the drill hole, - at least some of the parallel pipe piles are lifted at least partly out of the drill hole after the concrete has been cast, but before the concrete has bonded from a fluid concrete paste to a rigid one, when the concrete compacted in each drill hole to form a concrete pile expands laterally onto the concrete of the adjacent pipe pile and forms together with the concrete piles of the adjacent drill holes a unified watertight pile wall, characterized in that the drill holes are drilled using a drilling device with a reamer, and the pipe piles are non-rotating pipe piles equipped with longitudinal interlocks, of which interlocks one is a long interlocking member extending outside the diameter of the drilling device's reamer into the adjacent drill hole into the interlocking member of the adjacent pipe pile and the other a short interlocking member, to which the long interlocking member of the adjacent pipe pile attaches, which pipe piles are placed after the drilling device in each drill hole in connection with the drilling, which parallel pipe piles are joined together by the interlocks, and are smaller in diameter than the drill hole. - several essentially vertical drill holes are drilled side by side in the ground using a drilling device, - several pipe piles for casting are installed in a row into the drill holes, - the drill hole is flushed using a medium to remove drilling waste from the drill hole, - reinforcements are installed to reinforce the pile wall structure to be formed - concrete is cast into each pipe pile installed in the drill hole, - at least some of the parallel pipe piles are lifted at least partly out of the drill hole after the concrete has been cast, but before the concrete has bonded from a fluid concrete paste to a rigid one, when the concrete compacted in each drill hole to form a concrete pile expands laterally onto the concrete of the adjacent pipe pile and forms together with the concrete piles of the adjacent drill holes a unified watertight pile wall, characterized in that the drill holes are drilled using a drilling device with a reamer, and the pipe piles are non-rotating pipe piles equipped with longitudinal interlocks, of which interlocks one is a long interlocking member extending outside the diameter of the drilling device's reamer into the adjacent drill hole into the interlocking member of the adjacent pipe pile and the other a short interlocking member, to which the long interlocking member of the adjacent pipe pile attaches, which pipe piles are placed after the drilling device in each drill hole in connection with the drilling, which parallel pipe piles are joined together by the interlocks, and are smaller in diameter than the drill hole.