To provide a jig for tools, which jig can improve workability when tools are mounted on a main spindle of an NC machine tool or a holder of a tool magazine, etc., and can improve mounting accuracy of the tools.

The jig 11 for tools comprises an adjusting section 40 for variably setting the projecting length H0 of the tool 4 to be held by a body 20 on the body 20 for holding the tool 4 so as to move forward and backward, and a gauge section 30 for indicating the projecting length H0 of the tool 4 to be held by the body 20 based on the forward and backward movement of the adjusting section 40. When the adjusting section 40 is moved forward and backward along the body 20 so that the gauge section 30 indicates the projecting length H0 of the required tool 4, the projecting length of the tool 4 held by the body 20 becomes the required projecting length H0'. The tool 4 having the required projecting length H0' is mounted on the holder 3 keeping the required projecting length H0' intact.