To provide a method for producing industrially useful HFO-1234yf while suppressing generation and carbonization of high-boiling substances by one reaction involving thermal decomposition using a raw material that is easily supplied.

There is provided a method for producing 2,3,3,3-tetrafluoropropene by synthesis reaction involving thermal decomposition from a raw material composition containing chlorodifluoromethane and 1,1-difluoroethylene in the presence of a thermal medium. The method for producing 2,3,3,3-tetrafluoropropene includes (a) a process in which 1,1-difluoroethylene is preliminarily mixed with 1 mole of chlorodifluoromethane at 0.001-10 moles, or they are respectively supplied to a reactor, and are made to stagnate in the reactor for a predetermined time, and (b) a process in which the thermal medium is supplied to the reactor and the raw material composition and the thermal medium are made contact with each other in the reactor.