The magnetoelectric (ME) coupling on spin-wave resonances in single-crystal Cu2OSeO3 was studied by a novel technique using electron spin resonance combined with electric field modulation. An external electric field E induces a magnetic field component μ0H(i)=γE along the applied magnetic field H with γ=0.7(1) μT/(V/mm) at 10 K. The ME coupling strength γ is found to be temperature dependent and highly anisotropic. γ(T) nearly follows that of the spin susceptibility J(M)(T) and rapidly decreases above the Curie temperature T(c). The ratio γ/J(M) monotonically decreases with increasing temperature without an anomaly at T(c).