  A new algorithm for computing the accurate values of quasinormal frequencies
of extremal Reissner-Nordstr\"{o}m black holes is presented. The numerically
computed values are consistent with the values earlier obtained by Leaver and
those obtained through the WKB method. Our results are more precise than other
results known to date.
  We also find a curious fact that the resonant frequencies of gravitational
waves with multi-pole index $l$ coincide with those of electromagnetic waves
with multi-pole index $l-1$ in the extremal limit.
