We have performed specific-heat measurements on the heavy-fermion superconductor URu2Si2 in magnetic fields up to 17.5 T. A sharp peak in the specific heat signals the antiferromagnetic transition at TN=17.5K, which shifts to lower temperatures in applied magnetic fields. In order to describe the specific heat below TN, we have used the characteristic features of the excitation spectrum measured by neutron scattering. The relative field dependence of the antiferromagnetic transition temperature TN and the energy gap Δ in the magnetic excitation spectrum can be described by a single scaling relation of the form [1−(B/B0)2]. The scaling field of 48.5 T is close to the metamagnetic transition field B*=40T, where the heavy-fermion state is suppressed.