A signal processing method and apparatus reducing distortion using divided signals differing in only amplitude by weighting an input signal by first weights ki (i=1 to 4) to obtain divided signals, performing the same signal processing f(x) on the divided signals, weighting the signal processed divided signals by second weights l1 (i=1 to 4), and adding the divided signals Vout1 to Vout4 weighted by the second weights. The first weights are k1=t, k2=−t, k3=1, k4=−1, while the second weights are l1=−1, l2=1, l3=t3, l4=−t3. Here, t=b/a (where a and b are different positive integers).