  We present the first study of the discrete $\beta$-function of the $ SU(3) $
gauge theory with 10 massless domain-wall fermions in the fundamental
representation. The renormalized coupling is obtained by the finite-volume
gradient flow scheme, and the discrete $\beta$-function is extrapolated to the
continuum limit by the step-scaling method. Our result of the discrete
$\beta$-function (with $ s = 2 $) suggests that this theory possesses an
infrared fixed point around $ g_c^2 \sim 7.0 $ for $ c = \sqrt{8t}/L = 0.3 $.
