The B meson decay modes B--Dpp; and B--D(*)pp; have been studied using 29.4 fb(-1) of data collected with the Belle detector at KEKB. The B;(0)--D(0)pp; and B;(0)--D(*0)pp; decays have been observed for the first time with branching fractions B(B;(0)--D(0)pp;)=(1.18+/-0.15+/-0.16)x10(-4) and B(B;(0)--D(*0)pp;)=(1.20(+0.33)(-0.29)+/-0.21)x10(-4). No signal has been found for the B+--D(+)pp; and B+--D(*+)pp; decay modes, and the corresponding upper limits at 90% C.L. are presented.