Many results of the researches on structures containing brackets have been published by various researchers, while there have been scarcely any experimental data which justify these results. The author was able to conduct the tests on a perfectly fixed beam by using an acrylic material. According to the test results, it was found that the portion at the brackets did not follow the results predicted by the beam theory and the calculation currently used with a changing section resulted in an overestimation of the rigidity at the brackets. Hence, in this case, it is desirable to replace the brackets by the assumed effective brackets, as described in the present paper, and calculate with a changing section of the new brackets. In the present paper, an approximate formula which had been obtained by introducing the idea of a span point was used to simplify the calculation on a fixed beam with brackets. It was also found, as a result of the tests, that a lightening hole in the bracket had small effect on the flexural rigidity of the bracket, while a change in a shape of the flange on the bracket had a remarkable effect.