In K.~Hieda, A.~Kasai, H.~Makino, and H.~Suzuki, Prog. Theor. Exp. Phys. textbf{2017}, 063B03 (2017), a properly normalized supercurrent in the four-dimensional (4D) $mathcal{N}=1$ super Yang--Mills theory (SYM) that works within on-mass-shell correlation functions of gauge-invariant operators is expressed in a regularization-independent manner by employing the gradient flow. In the present paper, this construction is extended to the supercurrent in the 4D $mathcal{N}=2$ SYM. The so-constructed supercurrent will be useful, for instance, for fine tuning of lattice parameters toward the supersymmetric continuum limit in future lattice simulations of the 4D $mathcal{N}=2$ SYM.