which operation of the sewing machine is to be stopped by recognizing such a visual indication by the light emitting diode 22 and such acoustic indication by the buzzer 23 therefore the operator engaged in sewing is able to know that a fresh supply of bobbin thread is needed thus it is possible to replenish the supply of bobbin thread before the residual amount of bobbin thread z is reached and before the operation of the sewing machine is stopped in order to prevent sewing operation from being stopped at an inconvenient sewing position the predetermined value z0 is input to the processing circuit 13 by the key input 12 in the same fashion as that of the predetermined value z a decision as to whether or not the value z 0 for bobbin yarn has been reached is made after steps m4 and m5 and before step m6 that is at step m5a as illustrated in the fig7 flowchart after the decision is made at step m5a that the value z 0 has been reached the light emitting diode 22 emits light and the buzzer 23 sounds at step m5b steps m1 m5 m6 and m7 correspond respectively to steps n1 n5 n6 and n7 explained with reference to fig3 and similar operations are performed in both series of steps the light emitting diode 22 and the buzzer 23 are both shown by virtual lines in fig1 and.