PURPOSE: To make a pipe horizontally maintainable in a state of having a clamper held tight by supporting both end sides along a direction of the pipe axial center of a joining object pipe by a slinging means, and installing a gradient adjusting means, variably adjusting the position of a body frame to a horizontal level.

CONSTITUTION: A body frame 7 is provided with a first clamper 8 holding a joining object pipe 1 on one side and a second clamper 8 holding a pipe 2 on the other, respectively. In addition, the first clamper 8 is clamped to the body frame 7, and the second clamper 9 is installed travelably in reciprocation in the pipe axial center direction. Also there is provided a gradient adjusting means 21 which is interposed between a sliging means 12 and the body frame 7 in particular, and variably adjusting a position of the body frame 7 to the horizontal level. With this constitution, when the body frame 7 is tilted, the position of the frame 7 is adjusted by the gradient adjusting means 21, and thereby centering of both these pipes 1, 2 themselves can be done in this way.