  A quantum critical point (QCP) of the heavy fermion Ce(Ru_{1-x}Rh_x)_2Si_2 (x
= 0, 0.03) has been studied by single-crystalline neutron scattering. By
accurately measuring the dynamical susceptibility at the antiferromagnetic wave
vector k_3 = 0.35 c^*, we have shown that the energy width Gamma(k_3), i.e.,
inverse correlation time, depends on temperature as Gamma(k_3) = c_1 + c_2
T^{3/2 +- 0.1}, where c_1 and c_2 are x dependent constants, in a low
temperature range. This critical exponent 3/2 +- 0.1 proves that the QCP is
controlled by that of the itinerant antiferromagnet.
