Using a data sample of 772×106 BB pairs collected on the Ï'(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e-collider, we report the observation of B0→ppπ+π- A nd the first observation of B+→ppπ+π0. We measure a decay branching fraction of (0.83±0.17±0.17)×10-6 in B0→ppπ+π-for Mπ+π-<1.22 GeV/c2 with a significance of 5.5 standard deviations. The contribution from B0→ppK0 is excluded. We measure a decay branching fraction of (4.58±1.17±0.67)×10-6 for B+→ppπ+π0 with Mπ+π0<1.3 GeV/c2 with a significance of 5.4 standard deviations. We study the difference of the Mpp distributions in B0→ppπ+π- A nd B+→ppπ+π0.