Disclosed are a fluorinating agent represented by the general formula (1): wherein R1 to R4 are a substituted or unsubstituted, saturated or unsaturated alkyl group or a substituted or unsubstituted aryl group, and can be the same or different; R1 and R2 or R3 and R4 can bond to form a ring including a nitrogen atom or a nitrogen atom and other hetero atoms; or R1 and R3 can bond to form a ring including a nitrogen atom or a nitrogen atom and other hetero atoms, for example: a preparation process of the fluorinating agent and a process for preparing fluorine compounds by reacting various compounds with the fluorinating agent. The invention has also disclosed that the fluorinating agent is very effective for fluorinating oxygen containing functional compounds.