We have developed a new technique for inclusive reconstruction of the energ
y of B hadrons. The excellent efficiency and resolution of this technique a
llow us to make the must precise determination of the b-quark fragmentation
function, using e(+)e(-) --> Z(0) decays recorded in the SLAG Large Detect
or experiment. We compared our measurement with the predictions of a number
of fragmentation models. We excluded several of these models and measured
the average scaled energy of weakly decaying B hadrons to be [x(B)] = 0.714
+/- 0.005(stat) +/- 0.007(syst) +/- 0.002 (model dependence).