A mounting accuracy measurement system of a component mounting line configured by arranging multiple component mounting machines along a board conveyance path configured to convey a circuit board , wherein each of the multiple component mounting machines is configured to switch between a production mode, in which a component is mounted on the circuit board that is conveyed in and then conveyed out, and a mounting accuracy measurement mode, in which a mounting accuracy measurement component is mounted at a predetermined position on a mounting accuracy measurement board to measure a mounting accuracy thereof, wherein, when the control modes of two or more component mounting machines , among the multiple component mounting machines , are the mounting accuracy measurement mode, the mounting accuracy measurement board is conveyed between at least the two or more component mounting machines along the board conveyance path so that the two or more component mounting machines measure the respective mounting accuracy by sequentially using the mounting accuracy measurement board , characterized in that each of the multiple component mounting machines is configured to switch to a pass mode in addition to the production mode and the mounting accuracy measurement mode, the pass mode being a mode in which a component is conveyed out without being mounted on a conveyed-in board; and wherein the component mounting machine in the mounting accuracy measurement mode is configured to convey out the mounting accuracy measurement board to the component mounting machine on the downstream side after completing the mounting accuracy measurement when the control mode of the component mounting machine on the downstream side is the pass mode. wherein each of the multiple component mounting machines is configured to switch between a production mode, in which a component is mounted on the circuit board that is conveyed in and then conveyed out, and a mounting accuracy measurement mode, in which a mounting accuracy measurement component is mounted at a predetermined position on a mounting accuracy measurement board to measure a mounting accuracy thereof, wherein, when the control modes of two or more component mounting machines , among the multiple component mounting machines , are the mounting accuracy measurement mode, the mounting accuracy measurement board is conveyed between at least the two or more component mounting machines along the board conveyance path so that the two or more component mounting machines measure the respective mounting accuracy by sequentially using the mounting accuracy measurement board , characterized in that each of the multiple component mounting machines is configured to switch to a pass mode in addition to the production mode and the mounting accuracy measurement mode, the pass mode being a mode in which a component is conveyed out without being mounted on a conveyed-in board; and wherein the component mounting machine in the mounting accuracy measurement mode is configured to convey out the mounting accuracy measurement board to the component mounting machine on the downstream side after completing the mounting accuracy measurement when the control mode of the component mounting machine on the downstream side is the pass mode. <EOS>