The invention relates to an automatic striping device with simple mechanism, low price and low failure rate, belonging to the textile mechanism. The automatic striping device comprises an outer casing, a tool-rest fixing seat which is fixedly arranged on the outer casing, a yarn-selection fixing seat, a connecting seat and a main shaft which is fixedly arranged between the yarn-selection fixing seat and the connecting seat on the outer casing. An upper end and a lower end of the main shaft oppositely revolve and are respectively sheathed with a collecting-cutting rotary block. An L-shaped control board is oppositely and rotationally sheathed between the upper and lower collecting-cutting rotary blocks on the main shaft. A groove is cut on the tool-rest fixing seat, a tool-rest board is oppositely and rotationally arranged in the groove, a tension-spring is connected with the tool-rest board and the other end of the tension-spring is fixed onto the outer casing. An arc-shaped connecting cut is arranged at the right end of the tool-rest board, and the rim of the connecting cut is greater than 50 percent of the arc. A link rod is connected in the connecting cut, the left end of the link rod is provided with a connecting head which is articulated with the connecting cut, and the connecting head and the connecting cut are on the same plane. The right end of the link rod clings to an expansion spring, and a resetting pin is arranged in the middle of the link rod and clings to the control board.