The invention relates to a zigzag sewing machine. The zigzag sewing machine is provided with a lower pipe seat, a lower shaft, a transmission mechanism and a rotating shuttle, wherein the lower shaftis connected to the transmission mechanism and rotates in the lower pipe seat with the X-axis direction as the axis, the lower shaft can drive an outer kettle of a rotating shuttle to rotate with theY-axis direction as the axis through the transmission mechanism, and the transmission mechanism is provided with a rotating shuttle seat, a bearing and a transmission part; the rotating shuttle seat is arranged in the Y-axis direction of the outer kettle and form a penetrating part arranged in the outer kettle, an accommodating space is formed between the penetrating part and the outer kettle, thebearing is positioned in the accommodating space, the transmission piece is connected to the outer part of the outer kettle, and the transmission piece, the bearing and the penetrating part are sequentially arranged from the outer part of the inner kettle to the inner part of the outer kettle; the end part volume of the lower pipe seat can be reduced along the Y direction through the assembling state of the rotating shuttle seat, the bearing, the outer kettle and the transmission part, so that the zigzag sewing machine can perform sewing operation of welt edge covering on shoes with smaller sizes.