A motor control system includes 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. The numerical control device includes 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. The first-type amplifier generates a drive current signal of a motor directly from the received PWM instruction. The second-type amplifier includes a third processor that calculates a PWM instruction from the received positional instruction.