To provide a jig for a shaft, which jig has a simple structure, and has a plurality of fixing directions, and can perform highly accurate fixing, and has excellent versatility.

Half split jig 5 is symmetry with respect to right and left direction, and grips a shaft having a diameter of a millimeter-order. The jig 5 has horizontal gripping grooves Mpara which are formed on the upper portions of opposed surfaces by narrowing the distance between them, and grip the shaft along its axis by horizontally placing the shaft thereon, and vertical gripping grooves Mvert formed at the central portions of the opposed surfaces C in the vertical direction. The horizontal gripping grooves Mpara are V-shape recessed streaks having the width between them so as to become wider upward and having a stepped structure alternately connecting the tilted surfaces and the vertical surfaces horizontally extending in the axial direction. The vertical gripping grooves Mvert form a nearly rhombus shape hole in a plane view formed in the vertical direction by opposing V shape grooves formed on the respective opposed surfaces. In this case, the V shape grooves are formed by curved surfaces in which both sides of the V shape are configured by slightly convex curves elongating in the vertical direction intact.