To release braking as necessary in the case where current feeding is broken.

In a braking device 1, a manually releasing projection part 17b of a release lever 17 projected from protect covers 37, 38 is manually moved in a F direction in a condition in which current carrying is broken, namely, in a condition in which a coil spring is locked with a stem member 2 and an a taper surface 6a of an external cylinder 6 by retracting a ball 5 to the taper surface 6a and then braking is carried out, and thereby, the ball 5 is uncoupled from the taper surface 6a. It is thus possible to release braking of a table.