NOVELTY - A flow path (1) is connected to a fluid inlet port (5). A spiral flow path (2) is connected to the flow path (1). The branched flow paths (4a-4e) are branched from different location on the spiral flow path. The branched flow paths are connected to a flow path (3). A fluid exit port (6) is connected to the flow path (3).    USE - Fluid mixer for use in apparatus capable of measuring concentration of substance such as water, pH adjuster, liquid manure, bleaching agent, disinfectant, surfactant, chemical liquid, coagulant, waste liquid, petroleum, oil additive, adhesive agent, hardening agent, resin, solvent, coloring agent, foodstuff raw material, food additive, seasoning, microorganism, air, combustible gas, nonflammable gas, steam and synthetic intermediate (all claimed) used in various industries such as chemical industry, foodstuff industry, medical industry, semiconductor manufacturing industry and bio field. Uses include but are not limited to industrial water, distilled water, tap water, hydrochloric acid, sulfuric acid, nitric acid, agricultural liquid fertilizer, excrement, sodium hypochlorite, sodium percarbonate, chlorinated lime, ethanol, monoalkyl sulfate, alkyl amine oxide, wash facing material, milky lotion, kerosene oil, light oil, stability agent, filler, liquid resin, acrylic resin type adhesive, polyamine, acid anhydride, molten resin, iron oxide red, carbon black, beer, wine, tea, juice, honey, brown sugar, starch syrup, vinegar, bean paste, yeast, fungi, propane, ammonia, carbon dioxide, argon gas, etc.    ADVANTAGE - The fluid mixer can mix the fluid uniformly without any variation in concentration or temperature distribution in the flow direction of the fluid. The generation of defect by the change of chemical concentration is prevented. The size of the flow path is reduced hence the size of the fluid mixer is reduced and the installation space of the fluid mixer is reduced. The installation of the pipe is performed easily in the short period of time.    DETAILED DESCRIPTION - The flow path (3) is formed at the spiral center axis of the main portion. The communication holes are formed so that the flow path (3) and spiral channel are connected. The outer peripheral surface of the main portion is fixed to the casing. The spiral flow paths are formed in the internal peripheral surface of the casing. The spiral flow path is formed so that the passage sectional area is gradually reduced from the one end portion connected to the flow path (1) towards other end portion. The diameter of internal peripheral surface of the flow path (3) is gradually increased from the upstream side towards the fluid exit side. A ferrule coupling portion is provided in the casing. The flange portion is fixed by the clamp. The diameter reducing portion is provided in the outer periphery of a cylindrical portion of the housing. The main portion is inserted into the flange side opening of the cylindrical portion of the casing. The inlet port flow path and exit flow path are connected to a cavity formed in the casing. A cover covers the cavity formed in the casing. An INDEPENDENT CLAIM is included for apparatus capable of measuring substance concentration, which has the fluid mixer that is arranged in downstream side of the substance flowing line. The concentration and blend ratio of the substance are homogenized using the fluid mixer.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the fluid mixer.    Flow paths (1,3)    Spiral flow path (2)    Branched flow paths (4a-4e)    Fluid inlet port (5)    Fluid exit port (6)