To provide a spacer for slitter and its manufacturing method which suppresses the change of form with the passage of time, as well as has a light weight.

A billet of 500mm in diameter is forged and extended into a rod member, and after cutting the rod member, it is processed into a cylindrical member 3. The cylindrical member 3 is inserted to a female mold 4, the cylindrical member 3 is pressed by a male mold 5, and it is forged in a backward extruding process. As a result, the cylindrical member 3 is metal flowed, and raised in the female mold 4 to be made into a pipe member. The obtained pipe member is cut, so as to obtain a spacer product whose metal flowing direction is in the axial direction. Since the spacer has the maximum strength to the axial direction of the spacer, the change with the passage of time of the spacer is prevented, even though it is exposed to a strong fastening force. And since the residual stress of the spacer is released along the axial direction of the spacer, the deforming amount of a hole for installing the spacer is very small, even when the spacer is deformed, and the spacer can be installed to an installing shaft.