  We derive a general formula of an index for N = 2 superconformal field
theories on S1 \times S3 with insertions of BPS Wilson line or 't Hooft line
operator at the north pole and their anti-counterpart at the south pole of S3.
One-loop and monopole bubbling effects are taken into account in the
computation. As examples, we calculate the indices for N = 4 theories and N = 2
SU(2) theory with Nf = 4, and find good agreements between indices of line
operators related by S-duality. The relation between Verlinde loop operators
and the indices is explored. The holographic correspondence between the
fundamental (anti-symmetric) Wilson line operator and the fundamental string
(D5 brane) in AdS5\timesS5 is confirmed by the index comparison.
