Microcrystalline diamonds were successfully deposited on an abraded molybdenum surface under a magnetic field using a combustion flame of acetylene (C2H2) and oxygen (O2) gases. The deposition rate was about 1 &mgr;m/min, which is an order larger than that obtained by conventional chemical‐vapor‐deposition methods. The magnetic field led to an increase of the deposited area and of the microcrystal diameter. The microcrystals show good crystallinity as observed from scanning electron microscopy, reflective electron diffraction, and x‐ray diffraction measurements.