Provided is a water-soluble working fluid for a fixed abrasive grain wire saw, which can suppress an increase in viscosity when contamination by chips occurs and suppress the occurrence of clogged piping or firm sticking in equipment caused by contamination by chips; the foregoing is achieved by containing (C) a carbonic acid, (D) a compound that is basic when dissolved in water and (E) water, having an electrical conductivity at 25 DEG C of not lower than 300 [mu]S/cm and not higher than 3000 [mu]S/cm, having a pH at 25 DEG C of not lower than 5 and not higher than 10, and having a viscosity of a pseudo-working liquid of less than 30 mPa DEG s at 25 DEG C, where the pseudo working liquid is formed by adding 10 mass % of silicon grains having an average particle diameter of 1.5 [mu]m and then stirring.