Collapse behavior of spatial rigid steel frame while vertical load at one place of the beam continues to increase gradually is investigated experimentally and numerically. The spatial frame consists of four columns and four beams. Lateral buckling of the H-shaped beam induced the collapse of frame. The tips of both square tube columns supporting the beam were drawn inward. The center of the beam was twisted and at the portion the plastic hinge was formed by weak axis bending. The torsion or sway behavior of frame was hardly observed in this study. The experimental results of small steel frames are illustrated that the numerical prediction by the elasto-plastic beam-column FEM developed by the authors has adequate precision.