  On the basis of a simultaneous description of the isoscalar s-wave of
$\pi\pi$ scattering (from the threshold up to 1.9 GeV) and of $\pi\pi\to
K\bar{K}$ process (from the threshold to $\sim$ 1.4 GeV) in the
model-independent approach, it is shown that there exists the $f_0(665)$ state
with properies of the $\sigma$-meson, the glueball nature of $f_0(1500)$ is
indicated, and the $f_0(1370)$ is assigned mainly to $s{\bar s}$ state. The
coupling constants of the observed states with $\pi\pi$ and $K\bar{K}$ systems
and scattering lengths $a_0^0(\pi\pi)$ and $a_0^0(K\bar{K})$ are calculated.
The existence of the $f_0(665)$ state and the obtained $\pi\pi$-scattering
length ($a_0^0\approx 0.27 m_{\pi^+}^{-1}$) seem to suggest the linear
realization of chiral symmetry.
