To suppress the axial length of an inclined wall part of a tip reduced cylindrical part while ensuring the axial length of an exhaust gas purifying catalyst, and to suppress generation of machining defects such as wrinkles on the inclined wall part of the tip reduced cylindrical part.

In a manufacturing method of a storage case of an exhaust gas purifying catalyst 80, a metal cylindrical body 1 haring one end 1a and the other end c extended in the direction of the axial P1 to form an opening and its inner part forming catalyst storage space 1d is spinning-formed using a tool, a stepped shoulder part 15 which is along the direction orthogonal to the axis P1 of the cylindrical body 1 and opposite to an end part 80e of the exhaust gas purifying catalyst 80 or a holding member 83 is formed on one end 1a side of a circumferential wall of the cylindrical body 1, the shoulder part 15 is contracted from a small diameter part to an opening of one end 1a, and a tip contracted cylindrical part 14 having an inclined wall part 14a inclined to the axis P1 of the cylindrical body 1 is formed.