General formulas for decay widths of heavy mesons with arbitrary spin and parity to the heavy meson ground state plus a \ensuremath{\pi} or K are derived in the leading order of the 1/M expansion in the relativistic BS equation. Numerical results for various partial decay widths of ${1}^{+}$, ${2}^{+}$ doublets in the D, ${\mathit{D}}_{\mathit{s}}$, B, and ${\mathit{B}}_{\mathit{s}}$ series are obtained with a kernel used previously to obtain the spectra of low-lying states in these series, in good agreement with experiments. The results are in satisfactory agreement with the experimental data when they are available.