In this paper, the behavior of joint panels at the connection of rectangular steel column and two H-shaped beams with different depth are reported. The equilibrium equation of panel and the equation to calculate the stiffness of panel are indicated. And the equation to estimate the strength of panel is proposed. This equation is derived from two collapse mechanisms of the connection of column and beam. On a mechanism, only panel yields. This mechanism is the same one in case of standard panel. On the other mechanism, a part of panel, beam flange and beam web yield. The panel strength derived from the latter mechanism is lower than the strength derived from the former. In order to confirm the suitability of these equations, the loading tests of cruciform subassemblages were carried out. The strength and collapse mechanism derived from calculation were in good agreement with the results of test.