PURPOSE: To assemble a crank shaft in a thoroughly finished state and to omit finishing by press fitting and fixing a sleeve which fits into the inside peripheral surface of a crank web and the outside peripheral surface of a crank journal between said web and journal.

CONSTITUTION: The inside peripheral surface of a crank web 1 is formed to a tapered surface. A sleeve 3 of which the inside peripheral surface fits onto the outside peripheral surface of a crank journal 2 and the outside peripheral surface fits into the inside peripheral surface of the web 1 is formed. Such sleeve 3 is press fitted into the space between the web 1 and the journal 2 to fix both. The web 1 and the journal 2 are thus assembled in a thoroughly finished state, whereby finishing after assembly by shrinkage fit is omitted. The need for a large sized special lathe is thus eliminated.