A method of manufacturing a tape-formed oxide superconductor, in which a tape-formed wire material (6 in FIG. 1) is extended between a pair of reels (5a and 5b). Besides, a reactive gas is supplied form the gas supply ports of a reactive gas supply pipe (3a) vertically to the upper side film surface of the tape-formed wire material (6), so as to react the film body of this tape-formed wire material into a superconducting layer, while at the same time, a gas after the reaction is discharged from the gas discharge ports of discharge pipes (4a and 4b) for discharging the gas after the reaction. Likewise, the reactive gas is supplied vertically to the lower side film surface of the tape-formed wire material (6), so as to react the film body of this tape-formed wire material into a superconducting layer, while at the same time, the gas after the reaction is discharged from the gas discharge ports of discharge pipes (4c and 4d) for discharging the gas after the reaction. Even when the tape-formed wire material (6) is large in area, the tape-formed oxide superconductor has superconducting characteristics being uniform in it widthwise direction, and it can be manufactured at high speed.