PURPOSE: To correspond to multiformity of specification of a mounting frame in use for general purpose by providing a moving frame liftably fixed in a perpendicular direction, rotary frame supported rotatably by the moving frame and a supporting plate fixed to the rotatry frame with a space adjustable, and by connecting the mounting frame fixed to the supporting frame.

CONSTITUTION: In this assembling jig for fixing a horizontal part 2a to a fixed base 21 to also support a tilt part 2b in an opposite side to this horizontal part 2a by using an assembling jig 5, after adjusting a space of a supporting plate 17 corresponding to a width of a truss, a rear end of the tilt part 2b is fixed to the supporting plate 17 through a connecting member 18. By rotating a rotary frame 13 to adjust a tilt of the tilt part 2b and also height of a moving frame 8, an upper floor part truss 2 can be fixed under a condition quite the same to a set up condition. Similarly of mounting frames 1, a lower floor part truss is fixed. Thus, since the assembling jig 5 can correspond to changing specification of an escalator, use for general purpose can be attained.