  Decay constants of the charged and neutral pions in magnetic field are
considered in the framework of the effective quark-antiquark lagrangian
respecting Gell-Mann--Oakes--Renner (GOR) relations at zero field. The
$\sqrt{\frac{e_qB}{\sigma}}$ dependence is found in strong fields $e_qB\gg
\sigma$ for the neutral pion, while the charged pion constant decreases as
$\sqrt{\frac{\sigma}{e_qB}}$.
