We present a measurement of the time-dependent CP violation parameters in B0 -> eta'K-0 decays. The measurement is based on the full data sample containing 772 x 10(6) B (B) over bar pairs collected at the Upsilon(4S) resonance using the Belle detector at the KEKB asymmetric-energy e+e- collider. The measured values of the mixing-induced and direct CP violation parameters are: sin 2 phi(eff)(1) = +0.68 +/- 0.07 +/- 0.03, A(eta'K0) = +0.03 +/- 0.05 +/- 0.04, where the first uncertainty is statistical arid the second is systernatic. The values obtained are the most accurate to date. lurthierrimore. these results are consistent with our previous measurements and with the world-average value of sin 2 phi(1) measured in B-0 -> J/psi K-0 decays.