So far the agitatian of reaction vessel for photographic emulsion has been done empirically and habitually. Evaluation method of agitation efficiency by the use of photoelectric measurement of transmittance variations in the reaction vessel and its recording by pen-recorder was tested. 600 m l of 1% gelatine solution which contain 5.0 m l of 1 M KI solution at 38°C in 1000 m l tall-beaker was used as test solution, and 5.0 m l AgNO₃ was added quickly, and its transmittance variations were monitored with the lapse of time by photoelectric pen-recorder. By the addition of AgNO₃ solution, the transmittance of reaction vessel decrease suddenly and gradually increase again according to the agitation proceeding, and reach to definite value. The time interval of this process will be correspond to the agitation efficiency of each type of stirring rod. The agitation efficiencies of fourteen different types of stirring rods on various rotation speeds were tested by the above mantioned measuring method. These results are showed and discussed.