  We study the semileptonic branching fraction of $B$-meson into higher
resonance of charmed meson $D^{**}$ by using the Bjorken sum rule and the heavy
quark effective theory(HQET). This sum rule and the current experiment of
$B$-meson semileptonic decay into $D$ and $D^*$ predict that the branching
ratio into $D^{**}l\nu_l$ is about 1.7\%. This predicted value is larger than
the value obtained by the various theoretical hadron models based on the HQET.
