  We study the Schwinger effect in near-extremal Reissner-Nordstr\"{o}m (RN)
black holes with electric and/or magnetic charges in the (Anti-) de Sitter
(AdS) space. The formula for the Schwinger effect takes a universal form for
near-extremal black holes with the near-horizon geometry of ${\rm AdS}_2 \times
S^2$ and with the proper radii for the ${\rm AdS}_2$ space and the two-sphere
$S^2$, regardless of the asymptotically flat or (A)dS space. The asymptotic AdS
boundary enhances and the dS boundary suppresses the Schwinger effect and the
small radius of the AdS (dS) space reinforces the enhancement and suppression.
