Disclosed herein are a reaction method and a production method of an organic compound which are capable of achieving high reaction selectivity according to the purpose and a high production rate of a target substance. The methods include at least two fluids, wherein at least one kind of the fluids is a fluid containing at least one organic compound and at least one kind of the fluids other than the above fluid is a fluid containing at least one reactant in the form of a liquid or solution, and the respective fluids join together in a thin film fluid formed between processing surfaces arranged to be opposite to each other so as to be able to approach to and separate from each other, at least one of which rotates relative to the other, whereby an organic reaction is performed in the thin film fluid.