PROBLEM TO BE SOLVED: To provide a method for installing a steel sheet pile which can install a long steel sheet pile at a low cost and accurately without using a modified steel sheet pile and is hardly affected by meteorological and marine conditions.SOLUTION: When a plurality of permanent steel sheet piles 1,1... are driven into a foundation A so that the lengthwise direction is directed in the vertical direction and that the permanent steel sheet piles are arranged adjacent to each other in the width direction, a guiding steel sheet pile 2 shorter than the permanent steel sheet pile 1 is driven into a position in the foundation A into which the permanent steel sheet pile 1 is planned to be driven, directing the lengthwise direction in the vertical direction. Thereby guide holes 6,6... directed in the vertical direction are formed, after which the guiding steel sheet pile 2 is withdrawn, and in place of the withdrawn guiding steel sheet pile 2, the lower end side of the permanent steel sheet pile 1 is inserted in the guide hole 6 and installed, and the permanent steel sheet pile 1 is driven into a prescribed depth of the foundation A.