The device considered in this paper is a porous stud having microchannels running in three orthogonal directions, and was designed to enhance boiling heat transfer for liquid-cooled electronic components. The characteristics of boiling incipience at the microstructures on the porous stud were investigated. Experiments were performed to determine the temperature hysteresis during stepwise input of heater power Q to a simplified two-dimensional structure composed of parallel microchannels (cross section=0.3mm×0.5mm or 0.3mm×1.5mm). It was shown that wall superheating at incipience of boiling is almost independent of Q and channel cross section, remaining at a level of 10∼14K. Therefore, with increasing Q, temperature overshoot decreases. We also gave an analytical explanation, based on a transient heat conduction equation, for the mechanism of the incipience of boiling in the microchannels. Finally, using these results, the boiling incipience at the porous stud was explained.