The invention discloses a circumferential locking device comprising a revolving member having a fixed axial position; the revolving member can revolve around a first axis, and circumferentially provided with a locking structure; the circumferential locking device at least also comprises a locking piece, an operation piece and a bias assembly; the locking piece can axially approach the revolving member, and matches with the locking structure so as to lock the revolving member; the operation piece has a fixed axial position, and can rotate around the first axis in a preset angle; the bias assembly can apply force on the locking piece in a biased manner, so the locking piece can axially approach the revolving member; the operation piece is circumferentially provided with at least a first circumferential position and a second circumferential position; the first circumferential position allows the bias assembly to accumulate biased energy; the second circumferential position allows the bias assembly to release the accumulated energy. The invention also provides an output torque power tool having the circumferential locking device; the locking piece of the circumferential locking device can effectively lock or release the revolving member.