Many microdevices have been tested in order to enhance the interaction between vegetable oil and alcohol to raising the conversion into biodiesel. However, many microdevices have some complexities in manufacturing and/or operation process. Consequently, this work studied numerically the use of a Spiral-micromixer for mixing and reaction of Jatropha curcas oil and ethanol for the production of biodiesel. The simulated microdevices had 200 µm in height and width. The mixing of the fluid was analyzed with Reynolds numbers from 0.67 to 100 and reaction studies were carried out for the same Reynolds numbers and a residence times ranging from 0.2 to 1,000 s. The Spiral-micromixer showed the highest mixing between the oil and ethanol. The highest conversion of vegetable oil in biodiesel was obtained with the T-micromixer (average of 51.8 %) and for the Spiral-micromixer (average of 50 %) for Reynolds number studied. An increment in residence time increased conversion, and the maximum conversion achieved was 98,48 % and 99,99 % for T-micromixer and Spiral-micromixer, respectively. The efficiency of mixing and reaction process can be increased and high conversion ratios obtained using this type of micromixer.