  We report broadband spectral properties of the high mass X-ray binary pulsar
SMC X-2 by using three simultaneous $NuSTAR$ and $Swift$/XRT observations
during its 2015 outburst. The pulsar was significantly bright, reaching a
luminosity up to as high as $\sim$5.5$\times$10$^{38}$~ergs~s$^{-1}$ in 1-70
keV range. Spin period of the pulsar was estimated to be 2.37 s. Pulse profiles
were found to be strongly luminosity dependent. The 1-70 keV energy spectrum of
the pulsar was well described with three different continuum models such as (i)
negative and positive power-law with exponential cutoff, (ii) Fermi-Dirac
cutoff power-law and (iii) cutoff power-law models. Apart from the presence of
an iron line at $\sim$6.4 keV, a model independent absorption like feature at
$\sim$27 keV was detected in the pulsar spectrum. This feature was identified
as a cyclotron absorption line and detected for the first time in this pulsar.
Corresponding magnetic field of the neutron star was estimated to be
$\sim$2.3$\times$10$^{12}$ G. The cyclotron line energy showed a marginal
negative dependence on the luminosity. The cyclotron line parameters were found
to be variable with pulse phase and interpreted as due to the effect of
emission geometry or complicated structure of the pulsar magnetic field.
