To provide the numerical controller which has its communication protocol optimized and is high in data transmission efficiency.

A numerical control part 50 and servo amplifiers 61, 62, 63... are connected in daisy chain form by 1st serial communication lines 80, 81, 82, 83.... Then a current value, a PWM command value, a speed value, a position detected value, etc., are communicated. Further, the numerical control part 50 and a spindle amplifier 68 are connected together by a 2nd serial communication line 90. Then a speed command value, a torque value, etc., are communicated. Consequently, this constitution provides efficient data transmission whose communication protocol is optimized.