PURPOSE: To obtain a weight grader capable of automatically grading the weight of a live fish with a high grading accuracy.

CONSTITUTION: The weight grader is obtained by installing a housing container revolving means for revolving plural housing containers 9 housing live fishes one by one, setting plural fish releasing positions (A), (B), (C), (D) and (E) in the revolving passage of the housing containers 9 with the housing container revolving means, providing a weight measuring part 19 for measuring the weight of the live fishes housed in the housing containers 9, further installing fish releasing means 12, 13, 14, 15 and 16 for operating at any of the plural fish releasing positions (A), (B), (C), (D) and (E) according to the weight of the live fishes and releasing the live fishes to the outside of the housing containers 9 and simultaneously providing a fish release controlling means for controlling the operation of the fish releasing means 12, 13, 14, 15 and 16 based on the weight of the live fishes, the preset grading standard and the manner of setting the fish releasing positions (A), (B), (C), (D) and (E).