To provide a bolt and nut which can quickly alter relative positions without rotating the bolt and/or the nut in relative relation.

The bolt/nut A comprises: a bolt 1 on the periphery of which a spiral groove(s) of single, double, or more threads is or are formed for fitting and rolling balls; and a nut 2, engaging threadably with the bolt 1, which includes a ball retention case 21 threadably and relatively rotatably engaged around the bolt, a ball retention outer case 22 fitted around the ball retention case, and an outer case 23 fitted relatively rotatably around the ball retention outer case and further a primary locking device 24 which blocks the relative rotation between the ball retention case and the outer case, wherein the ball retention case is rotatably fitted against ball fitting holes 211 arranged spirally at given intervals according to the spiral groove and has a plurality of balls 212 in part against the spiral groove 11, and wherein the ball retention outer case are supporting balls by sandwitching with the spiral grooves.