A method of manufacturing a housing of a passenger air bag comprising: a material preparation step of preparing first and second fiber reinforced composite materials (T1, T2); and a press-forming step of cross-plying and then press-forming the first and second fiber reinforced composite materials to form the housing of a passenger air bag, wherein, in the material preparation step, the first and second fiber reinforced composite materials include a reinforcing fiber and a thermoplastic resin, and the first and second fiber reinforced composite material are prepared using at least one of the group consisting of a continuous fiber reinforced thermoplastic, a long fiber reinforced thermoplastic, and a short fiber reinforced thermoplastic, wherein the first and second fiber reinforced composite materials are in a sheet shape, wherein, in the press-forming step, the first and second fiber reinforced composite materials are heated to a predetermined temperature and placed between upper and lower molds (11, 13) of a press mold, and the upper and lower molds are pressed against each other, thereby forming the housing of a target shape from the first and second fiber reinforced composite materials, and characterised in that cross-plying the first and second fiber reinforced composite materials comprises arranging one of the first or second fiber reinforced composite materials in a length direction of the housing, and arranging the other of the first or second fiber reinforced composite materials in a width direction of the housing, wherein the first and second fiber reinforced composite materials are stacked on top of the other to be overlapped at a central region except for both ends of the length direction of the housing, and the overlap ratio is adjusted. a material preparation step of preparing first and second fiber reinforced composite materials (T1, T2); and a press-forming step of cross-plying and then press-forming the first and second fiber reinforced composite materials to form the housing of a passenger air bag, wherein, in the material preparation step, the first and second fiber reinforced composite materials include a reinforcing fiber and a thermoplastic resin, and the first and second fiber reinforced composite material are prepared using at least one of the group consisting of a continuous fiber reinforced thermoplastic, a long fiber reinforced thermoplastic, and a short fiber reinforced thermoplastic, wherein the first and second fiber reinforced composite materials are in a sheet shape, wherein, in the press-forming step, the first and second fiber reinforced composite materials are heated to a predetermined temperature and placed between upper and lower molds (11, 13) of a press mold, and the upper and lower molds are pressed against each other, thereby forming the housing of a target shape from the first and second fiber reinforced composite materials, and characterised in that cross-plying the first and second fiber reinforced composite materials comprises arranging one of the first or second fiber reinforced composite materials in a length direction of the housing, and arranging the other of the first or second fiber reinforced composite materials in a width direction of the housing, wherein the first and second fiber reinforced composite materials are stacked on top of the other to be overlapped at a central region except for both ends of the length direction of the housing, and the overlap ratio is adjusted.