  Prepotentials in N=2 supersymmetric Yang-Mills theories are known to obey
non-linear partial differential equations called
Witten-Dijkgraaf-Verlinde-Verlinde (WDVV) equations. In this paper, the
prepotentials at one-instanton level in N=2 supersymmetric SU(4) Yang-Mills
theory are studied from the standpoint of WDVV equations. Especially, it is
shown that the one-instanton prepotentials are obtained from WDVV equations by
assuming the perturbative prepotential and by using the scaling relation as a
subsidiary condition but are determined without introducing Seiberg-Witten
curve. In this way, various one-instanton prepotentials which satisfy both WDVV
equations and scaling relation can be derived, but it turns out that among them
there exist one-instanton prepotentials which coincide with the instanton
calculus.
