  Observations of the 21 cm line radiation coming from the epoch of
reionization have a great capacity to study the cosmological growth of the
Universe. Also, CMB polarization produced by gravitational lensing has a large
amount of information about the growth of matter fluctuations at late time. In
this thesis, we investigate their sensitivities to the impact of neutrino
property on the growth of density fluctuations, such as the total neutrino
mass, the neutrino mass hierarchy, the effective number of neutrino species
(extra radiation), and the lepton asymmetry of our Universe. We will show that
by combining the precise CMB polarization observations with Square Kilometer
Array (SKA) we can measure the impact of non-zero neutrino mass on the growth
of density fluctuation, and determine the neutrino mass hierarchy at 2 sigma
level if the total neutrino mass is smaller than 0.1 eV. Additionally, we will
show that by using these combinations we can constrain the lepton asymmetry
better than big-bang nucleosynthesis (BBN). Besides we discuss constraints on
that in the presence of some extra radiation, and show that the 21 cm line
observations can substantially improve the constraints obtained by CMB alone,
and allow us to distinguish the effects of the lepton asymmetry from those of
extra radiation.
