A flatbed knitting machine provided with: a yarn feeding means for feeding a knitting yarn to knitting needles that operate for knitting a fabric whose feeding condition is controllable; a control means for calculating the knitting yarn length necessary for knitting the fabric every predetermined knitting cycle in accordance with the knitting data of the fabric and at the same time for controlling the supply condition of the yarn feeding means; a measuring means for measuring the length of the knitting yarn fed from the yarn feeding means to the knitting needles; an adjusting means for comparing the length of the knitting yarn fed to the knitting needles measured by the measuring means with a calculated result of the control means every knitting cycle and performing the stitch adjustment in accordance with the comparison results; and a buffer means comprising a buffer arm installed to a feeding route of knitting yarn from the yarn feeding means to the knitting needles, for temporarily storing the knitting yarn in a predetermined length range this being accompanied by a change of a tilt angle of the buffer arm, the tilt angle corresponding to the tension, wherein the control means controls to start the yarn feeding condition of the yarn feeding means set to a necessary yarn feeding mode that feeds the knitting yarn of the length that corresponds to the calculated result every knitting cycle, and at the same time, monitors the buffer means, and when the tilt angle of the buffer arm exceeds a predetermined range in the midst of the knitting cycle started in the necessary yarn feeding mode, as remedial process, changes over the knitting yarn feeding condition of the yarn feeding means during the remaining period of the knitting cycle to a buffer condition mode that controls the state change of the buffer means to satisfy a predetermined condition, characterized in that the measuring means measures lengths of the knitting yarn between a beginning phase and an ending phase, necessary for the control in both of the necessary yarn feeding mode and the buffer condition mode every knitting cycle, and in case of the control means changes over the yarn feeding condition of the yarn feeding means from the necessary yarn feeding mode to the buffer condition mode in the midst of the knitting cycle, the adjusting means compares the length of the knitting yarn measured between the beginning phase and the ending phase for the buffer condition mode in the relevant knitting cycle to the length of the knitting yarn that corresponds to the calculated result of the control means and performs stitch adjustment. a yarn feeding means for feeding a knitting yarn to knitting needles that operate for knitting a fabric whose feeding condition is controllable; a control means for calculating the knitting yarn length necessary for knitting the fabric every predetermined knitting cycle in accordance with the knitting data of the fabric and at the same time for controlling the supply condition of the yarn feeding means; a measuring means for measuring the length of the knitting yarn fed from the yarn feeding means to the knitting needles; an adjusting means for comparing the length of the knitting yarn fed to the knitting needles measured by the measuring means with a calculated result of the control means every knitting cycle and performing the stitch adjustment in accordance with the comparison results; and a buffer means comprising a buffer arm installed to a feeding route of knitting yarn from the yarn feeding means to the knitting needles, for temporarily storing the knitting yarn in a predetermined length range this being accompanied by a change of a tilt angle of the buffer arm, the tilt angle corresponding to the tension, wherein the control means controls to start the yarn feeding condition of the yarn feeding means set to a necessary yarn feeding mode that feeds the knitting yarn of the length that corresponds to the calculated result every knitting cycle, and at the same time, monitors the buffer means, and when the tilt angle of the buffer arm exceeds a predetermined range in the midst of the knitting cycle started in the necessary yarn feeding mode, as remedial process, changes over the knitting yarn feeding condition of the yarn feeding means during the remaining period of the knitting cycle to a buffer condition mode that controls the state change of the buffer means to satisfy a predetermined condition, characterized in that the measuring means measures lengths of the knitting yarn between a beginning phase and an ending phase, necessary for the control in both of the necessary yarn feeding mode and the buffer condition mode every knitting cycle, and in case of the control means changes over the yarn feeding condition of the yarn feeding means from the necessary yarn feeding mode to the buffer condition mode in the midst of the knitting cycle, the adjusting means compares the length of the knitting yarn measured between the beginning phase and the ending phase for the buffer condition mode in the relevant knitting cycle to the length of the knitting yarn that corresponds to the calculated result of the control means and performs stitch adjustment.