We report an improved measurement of the partial-rate CP asymmetry in B±→K0π± decays. The analysis is based on a data sample of 85×106 BB̄ pairs collected at the Y(4S) resonance with the Belle detector at the KEKB e +e- storage ring. We measure ACP(K 0π±) = 0.07-0.08 +0.09 +0.03 +0.01, where the first and second errors are statistical and systematic, respectively; the corresponding 90% confidence-level interval is -0.10