The invention relates to an edge alignment device for a sewing machine. The edge alignment device comprises a support, a rotating shaft, an edge distance switching wheel, a first switching position ejecting block, a second switching position ejecting block and an edge alignment positioning piece. The rotating shaft is supported on the support and has a sliding degree of freedom and a one-way rotating degree of freedom relative to the support. The edge alignment positioning piece is installed at the rear end of the rotating shaft. The edge distance switching wheel is connected to the front end of the rotating shaft in a fastened mode, and the part, between the edge distance switching wheel and the support, of the rotating shaft is sleeved with a spring. A first positioning ejecting block and a second positioning ejecting block are connected to the front end of the support. The edge distance switching wheel comprises an inner wheel rim and an outer wheel rim, at least one trapezoidal first protruding block stretching forwards is arranged at the front end of the inner wheel ring, triangular protrusions are arranged at the front ends of the first protruding blocks, and the side faces of the first protruding blocks form a sliding rail for the first positioning ejecting block to slide; at least one trapezoidal second protruding block stretching forwards is arranged at the front end of the outer wheel ring, triangular protrusions are arranged at the front ends of the second protruding blocks, and the side faces of the second protruding blocks form a sliding rail for the second positioning ejecting block to slide.