To provide a guide pulley capable of optionally adjusting the winding angle of a wire saw with an object to be cut or the guided paying-out direction of the wire saw, without catching a foreign matter between the object and the grounding area of a trestle.

This guide pulley guides the wire saw W in a specified direction, in a wire sawing technique, and is equipped with the trestle 1 to be fixed to the object S to be cut, a plurality of fixed pulleys 2 which are pivotally supported, in a freely horizontally rotatable manner, within a parallel area with a base plate (grounding area) 1a of the trestle 1, a pair of right/left swing arms 4, 4' fixed, in such a manner that their oblique movement is adjustable, on both right/left sides of the trestle 1 with the fixed pulleys 2 sandwiched in between them and movable pulleys 3 having support shafts 12 in the direction where the swing arms 4, 4' are obliquely movable, installed in a freely rotatable manner.