  A precise measurement of the vector and axial-vector form factors difference
$F_V-F_A$ in the $K^+\rightarrow{\mu^+}{\nu_{\mu}}{\gamma}$ decay is presented.
About 95K events of $K^+\rightarrow{\mu^+}{\nu_{\mu}}{\gamma}$ are selected in
the OKA experiment. The result is $F_V-F_A=0.134\pm0.021(stat)\pm0.027(syst)$.
Both errors are smaller than in the previous $F_V-F_A$ measurements.
