  In a force-free magnetic field, there is no interaction of field and the
plasma in the surrounding atmosphere i.e., electric currents are aligned with
the magnetic field, giving rise to zero Lorentz force. The computation of many
magnetic parameters like magnetic energy, gradient of twist of sunspot magnetic
fields (computed from the force-free parameter $\alpha$), including any kind of
extrapolations heavily hinge on the force-free approximation of the
photospheric magnetic fields. The force-free magnetic behaviour of the
photospheric sunspot fields has been examined by \cite{metc95} and
\cite{moon02} ending with inconsistent results. \cite{metc95} concluded that
the photospheric magnetic fields are far from the force-free nature whereas
\cite{moon02} found the that the photospheric magnetic fields are not so far
from the force-free nature as conventionally regarded. The accurate
photospheric vector field measurements with high resolution are needed to
examine the force-free nature of sunspots. We use high resolution vector
magnetograms obtained from the Solar Optical Telescope/Spectro-Polarimeter
(SOT/SP) aboard Hinode to inspect the force-free behaviour of the photospheric
sunspot magnetic fields. Both the necessary and sufficient conditions for
force-freeness are examined by checking global as well as as local nature of
sunspot magnetic fields. We find that the sunspot magnetic fields are very
close to the force-free approximation, although they are not completely
force-free on the photosphere.
