  We have performed transverse-field muon spin relaxation (TF-$\mu$SR)
measurements on ambient-pressure-grown polycrystalline
$\mathrm{LaO_{0.5}F_{0.5}BiS_{2}}$. From these measurements, no signature of
magnetic order is found down to 25 mK. The value of the magnetic penetration
depth extrapolated to 0 K is 0.89 (5) $\mu$m. The temperature dependence of
superconducting penetration depth is best described by either a multigap s +
s-wave model with $\Delta_{1}$ = 0.947 (7) meV and $\Delta_{2}$ = 0.22 (4) meV
or the ansiotropic s-wave model with $\Delta(0)$ = 0.776 meV and anisotropic
gap amplitude ratio $\Delta_{min}/\Delta_{max}$ = 0.34. Comparisons with other
potentially multigap $\mathrm{BiS_{2}}$-based superconductors are discussed. We
find that these $\mathrm{BiS_{2}}$-based superconductors, including
$\mathrm{Bi_{4}O_{4}S_3}$ and the high-pressure synthesized
$\mathrm{LaO_{0.5}F_{0.5}BiS_{2}}$, generally conform to the Uemura relation.
