We present measurements of B + → D* 0 τ + ν τ and B + → D 0 τ + ν τ decays in a data sample of 657 × 10 6 BB pairs collected with the Belle detector at the KEKB asymmetric-energy e + e - collider. We find 446 +58 -56 B + → D* 0 τ + ν τ events with a significance of 8.1 standard deviations, and 146 +42 -41 B + → D 0 τ + ν τ events with a significance of 3.5 standard deviations. The latter signal provides the first evidence for this decay mode. The measured branching fractions are B(B + → D* 0 τ + ν τ ) = (2.12 +0.28 -0.27 (stat) ± 0.29(syst))% and B(B + →D 0 τ + ν τ )-(0.77±0.22(stat)±0.12(syst))%.