To provide a process to produce 1,1-dichloro-2,3,3,3-tetrafluoropropene (CFO-1214ya) simply and economically without requiring purification of 1,1-dichloro-2,2,3,3,3-pentafluoropropane (HCFC-225ca) from the raw material component obtained as a mixture of isomers, i.e. dichloropentafluoropropane (HCFC-225) including HCFC-225ca and at the same time to produce simply and economically 2,3,3,3-tetrafluoropropene (HFO-1234yf) from 1-chloro-2,3,3,3-tetrafluoropropane (HCFC-244eb).A raw material composition comprising HCFC-244eb and HCFC-225 including HCFC-225ca is contacted with an alkali aqueous solution in the presence of a phase-transfer catalyst to produce CFO-1214ya from HCFC-225ca and at the same time to produce HFO-1234yf from HCFC-244eb.