A method of producing an organic silicon compound includes a step of reaction of the following: (A) a reactive silane compound represented by General Formula (1) below: R1mSiY(4-m) (wherein R1 is a monovalent organic group (except for the group represented by Y) or a hydrogen atom; Y indicates a chlorine atom or a group represented by —OR2; R2 indicates a monovalent hydrocarbon group having 1 to 30 carbon atoms; and m is a number in the range of 0 to 3), (B) a halogenated organic compound represented by General Formula (2) below: R3—X (wherein R3 indicates a monovalent organic group; and X is a halogen atom), and (C) metallic magnesium (Mg) in the presence of (D) an organic solvent containing at least one type of ether type compound.