PURPOSE: To make an accurate cut along the cutting slated line performable.

CONSTITUTION: In this wire saw method, two through holes 2, 3 are installed each in both upper and lower ends of a vertical cutting slated line L of a wall concrete structure 1. Next, a guide part 4 is set up in a front side of the structure 1. This guide part 4 is provided with a pair of guide plates 5, 6 going along the cutting slated line L and being clamped to the structure 1 so as to hold it between, and a pair of flexible plates 7, 8 attached tight to the front of these guide plates. The guide plates 5, 6 are composed of flat plates and their sides 5a, 6a being opposed in holding the cutting slated line L between are parallelly extended along the cutting slated line L. The flexible plates 7, 8 are attached tight to the guide plates 5, 6 in a cantilevering manner in an interval somewhat narrower than a diameter of a wire saw in holding the cutting slated line L between. When the wire saw is inserted into this part, these flexible plates 7, 8 are elastically deformed in the traveling direction of the wire saw at the inserted spot of the saw, thus they come into contact with a circumferential surface of the wire saw.