To provide a temperature controlling method for a wire saw, with which condensation is prevented from occurring and an efficient temperature controlling can be performed.

A cooling water fed from the outside a wire saw is branched in the main body of the wire saw 10 into two systems of feed lines or a low temperature line 48A and a temperature controlling line 48B. The cooling water running in the low temperature line 48A is distributed and fed to apparatuses, which are installed outside a working chamber 42 and do not trouble with condensation, such as a heat exchanger 38 and the like as it is or without the controlling its temperature. On the other hand, the cooling water running in the temperature controlling line 48B, after its temperature is controlled with a temperature controlling unit 50 up to a temperature higher than a dew point temperature, is distributed and fed to apparatuses, which are installed within the working chamber 42 and mindful of sweating, such as the bearing units 19A-19C of grooved rollers 18A-18C and the like. Thus, the condensation can be prevented from occurring, resulting in allowing to prevent an electric leakage from developing and a cutting accuracy from lowering.