Abstract: A repair method of a plate member disposed so as to separate a high-pressure space and a low-pressure space and having a cooling passage provided inside thereof along a surface thereof, comprising: removing a damaged portion generated in the plate member so as to expose the cooling passage; primarily filling an area where a material is removed so as to block the cooling passage and form an external shape of the plate member having no missing portion as compared to its original external shape; forming a first opening through which the cooling passage communicates with the low-pressure space on an upstream side, in a flow direction of a refrigerant in the cooling passage, of a position where the cooling passage is blocked; and forming a second opening through which the cooling passage communicates with the high-pressure space on a downstream side of the position where the cooling passage is blocked.