This thesis describes the measurement of the branching fraction of B to tau nu decays using the full data sample of the Japanese Belle experiment. The measurement uses the semileptonic tagging algorithm and gives a result of [1.25 ± 0.28(stat.) ± 0.27(syst.)] x 10^-4. Another topic described in this thesis is the development of a track-finding algorithm for the upcoming Belle 2 experiment.