PROBLEM TO BE SOLVED: To provide a collective breeding device of test small fish having excellent individual observation properties of each zebra fish although a large number of zebra fish can be bred with different conditions in a narrow space.SOLUTION: A large number of drawer-shaped water tanks 1 storing each zebra fish individually are supported in pockets of a frame 2 so as to slide. The pockets of the frame 2 are aligned in a large number in vertical and horizontal directions. At least a pair of side walls of the frame 2 are formed of transparent resin and a large number of lid covers cover upper openings of the respective drawer-shaped water tanks individually and detachably. A water supply unit 5 arranged adjacently on a depth side of the frame 2 has distribution water tanks in a large number of stages. The distribution water tank in each stage supplies water to the drawer shaped water tank 1 in the same stage. Water falls sequentially from the distribution water tank in an uppermost stage to the distribution water tank in a lowermost stage.SELECTED DRAWING: Figure 1
