Advances in micro-electro-mechanical systems (MEMS) resulted in the fabrication of electronic and optic devices which generate high amounts of heat in a small space. Microchannel heat sinks are a new type of heat exchangers which are capable to absorb such ultrahigh heat fluxes and ensure the proper function of such devices. In the present work, a microchannel heat sink made of ZrB2 ceramic is investigated numerically to evaluate its feasibility to operate at such harsh conditions. The governing equations of the liquid domain (water) and solid domain (ZrB2) were solved by the finite element method. The obtained results showed a considerable heat transfer rate from the heated surface. For example, at an ultra-high heat flux of 3.6 MW/m2, the maximum temperature didn't exceed ~360 K. The high heat transfer area per volume of the applied microchannel, as well as the remarkable thermal conductivity of ZrB2, are the main reasons for such a high heat transfer rate.