For examining lateral-torsional buckling behavior of H-shaped steel beam with concrete floor slab，numerical model with springs，which are considered with restraint effect by slab，on the beam upper flange is often used. This paper describes the restraint effect by slab on the beam，e.g.，torsional stiffness，lateral stiffness，maximum strength，and so on. First，loading test with slab-beam subassemblies was conducted to confirm the effects of some kinds of parameters on the stiffness and strength at the connection between beam upper flange and concrete slab. Second，prediction results by past researches and test results are compared，and in a part，new methods are proposed to enhance accuracy of prediction results.
