An analytical equation for the steady-state catalytic current of mediated bioelectrocatalysis has been derived as a function of the mediator concentration and the electrode potential for the case where the concentration of a substrate is sufficiently higher than the Michaelis constant for the substrate and the redox reaction of a mediator to obey the Nernst equation at an electrode surface. The equation can be reduced to the equations so far proposed for limited cases. The equation representing the limiting steady-state catalytic current as a function of the mediator concentration is useful to evaluate the catalytic constant of the enzyme and the Michaelis constant for the mediator, separately.