Fish grading is carried out to maintain fish size uniformity being farmed. In general, fish grading is still done traditionally. Traditional fish grading is estimated to have low effectiveness, including long grading times, low accuracy rates, andhigh fish stress levels. The purpose of this research is to design a fish grader machine in a prototype model and determine the effectiveness of the fish grader machine that was designed. Design of fish grader machine includes designing, manufacturing and testing the effectiveness of fish grader machines. The effectiveness of the fish grader machine was observed based on length of time grading and counting, the accuracy of fish size uniformity levels, and accuracy of fish counting levels. The design of the fish grader machine consists of four main components, namely a hopper as a fish motion feeder that was equipped with a door stopper, a rotating conical disc driven by a driving motor as a driving force and directing fish to the grader gap, a grader plate which was made in a circle as a grading breaker, and a container count as a fish count line that was equipped with infrared sensor based on a microcontroller (Arduino). The results of testing the effective fish grader machine obtained that the length of time for grading and counting was 0.54 seconds/fish, the accuracy of fish size uniformity was 94.40%, and the accuracy of fish counting was 94.20%