In genral the object of a bracketed connection is to increase the strength and rigidity of connected parts. For determining bracket sizes investigations of the stress distribution in the bracket and variations of the bending moment of structural members due to bracket sizes should be carried out. In this paper investigations of the stress distribution in brackets and economical shapes of brackets by photoelastic method are described in part I, and the theoritical analysis of bracketed beam in part II. Experiments were carried out on three kinds of series specimens. According to test results the stress in bracket is smaller than the stress in the adjacent member. But discontinuity at ends of the bracket brings about the stress conncentration, therefore special attentions must be taken about this matter. Furthermore the diameter and the position of centre of the circular hole in brackets were studied. On the theoritical investigation of the bracketed beam, the author adopted the two dimensional theory in the bracket part, and found the stress function which satisfies boundary condition at several points. From the results displacements in the bracketed beam and staically indeterminate quantities in the fix-end beam and so on were obtaind. It could be confirmed that theoritical values of the stress. coincide thoroughly with experimental values.