A flatbed knitting machine with a yarn feeding device, the flatbed knitting machine includes: at least two needle beds interleaving a needle bed gap to face each other in a front-back direction and having knitting needles to be lined up in a lengthwise direction; a carriage being capable of reciprocating along the lengthwise direction of the needle beds and being mounted with a knitting cam to sequentially select the knitting needles and to drive for knitting a knitted fabric; yarn feeder rails (2, 2a, 2b, 2c, 2d) being installed above the needle bed gap and having tracks (2aB, 2aF, 2bB,2bF) to extend in the lengthwise direction of the needle beds; wherein the carriage being provided with an entrainment pin which is capable of being engaged with an entrainment-type running member mounted on the track (2aB, 2aF, 2bB, 2bF) and causes the entraining-type running member to run while being engaged; and the yarn feeding device including a self-running-type running member (3, 3a, 3b) mounted on the track (2aB, 2aF, 2bB,2bF) and capable of running in the lengthwise direction on a part of a route formed by the track (2aB, 2aF, 2bB, 2bF) for feeding knitting yarn to the knitting needles: and the yarn feeding device comprises; a movement member (4, 4a, 4b) that has a movement part extending in the lengthwise direction, is arranged in parallel to an outer side of the track (2aB, 2aF, 2bB,2bF) in the front-back direction with a distance between the movement member (4, 4a, 4b) and the track; a coupling member (5, 5a, 5b) that couples the self-running-type running member (3, 3a, 3b) to the movement part; and a movement driving part (12, 12a, 12b) that is provided on an end portion of the yarn feeder rail (2, 2a, 2b, 2c, 2d) in the lengthwise direction and is capable of driving the self-running-type running member (3, 3a, 3b) to run on the track (2aB, 2aF, 2bB, 2bF) by driving the movement member (4, 4a, 4b) in the lengthwise direction and thereby moving the coupling member (5, 5a, 5b); characterized in that the self-running-type running member (3, 3a, 3b) mounted on the track (2aB, 2aF, 2bB, 2bF) can be interleaved in a distance in the front-back direction between the movement part of the movement member (4, 4a, 4b) and the track (2aB, 2aF, 2bB, 2bF). at least two needle beds interleaving a needle bed gap to face each other in a front-back direction and having knitting needles to be lined up in a lengthwise direction; a carriage being capable of reciprocating along the lengthwise direction of the needle beds and being mounted with a knitting cam to sequentially select the knitting needles and to drive for knitting a knitted fabric; yarn feeder rails (2, 2a, 2b, 2c, 2d) being installed above the needle bed gap and having tracks (2aB, 2aF, 2bB,2bF) to extend in the lengthwise direction of the needle beds; the yarn feeding device comprises; a movement member (4, 4a, 4b) that has a movement part extending in the lengthwise direction, is arranged in parallel to an outer side of the track (2aB, 2aF, 2bB,2bF) in the front-back direction with a distance between the movement member (4, 4a, 4b) and the track; a coupling member (5, 5a, 5b) that couples the self-running-type running member (3, 3a, 3b) to the movement part; and a movement driving part (12, 12a, 12b) that is provided on an end portion of the yarn feeder rail (2, 2a, 2b, 2c, 2d) in the lengthwise direction and is capable of driving the self-running-type running member (3, 3a, 3b) to run on the track (2aB, 2aF, 2bB, 2bF) by driving the movement member (4, 4a, 4b) in the lengthwise direction and thereby moving the coupling member (5, 5a, 5b); characterized in that the self-running-type running member (3, 3a, 3b) mounted on the track (2aB, 2aF, 2bB, 2bF) can be interleaved in a distance in the front-back direction between the movement part of the movement member (4, 4a, 4b) and the track (2aB, 2aF, 2bB, 2bF).