A motor control system in which one numerical control device controls a first-type amplifier without a DSP and a second-type amplifier with a DSP, and the cost of which has been reduced by reducing the number of interface circuits (serial bus control circuits) to be provided in the numerical control device has been disclosed. The system comprises a first-type amplifier that receives a PWM instruction, a second-type amplifier that receives a positional instruction, a numerical control device, and a serial bus, wherein the numerical control device comprises a first processor that calculates a positional instruction of a motor, a DSP that calculates a PWM instruction of the first-type amplifier from the positional instruction, and a serial bus control circuit that outputs the PWM instruction of the first-type amplifier and the positional instruction of the second-type amplifier to the serial bus, and the first-type amplifier generates a drive current signal of a motor directly from the received PWM instruction and the second-type amplifier comprises a third processor that calculates a PWM instruction from the received positional instruction.