To provide a shrink fitting method for a member capable of carrying out high precision assemblage by precisely positioning it against a jig without making contact with a standard surface required to maintain high precision against other members of the member to fit and install on a support axis.

A jig to hold a support axis is featured to have a bearing surface formed to be at required squareness against the support axis in its holding state and to install a member on the support axis by shrink fitting after making a parallel flat surface separated from the other member mounting standard surface of the member orthogonal in required precision against an axis of the support axis while there is a clearance between a hole and the support axis with the bearing surface and holding it in a shrink fitting method to install the member on the support axis by shrinkage of the member due to temperature fall by fitting the hole formed there against the support axis in a state of heating the member.