Single crystal diamond is expected to be a new material for not only micro machining tools but also innovative micro devices. In this paper, we demonstrate the micro-patterning of bulk diamond by exploiting thermochemical reaction between diamond and sidero-metals. We demonstrate micro-patterning of single crystal diamond by annealing at ∼1073 K after either micro-patterning nickel on the diamond or placing the diamond on a silicon substrate with a micro-patterned nickel layer. Etching rates ∼0.2μm/min were successfully achieved. We also experimentally elucidated the etching mechanisms and identified the dominant factors in the etching processes.