Abstract: A reinforcement device for side doors of automobiles, including an impact bar mounted to an outer panel by two brackets at both ends, and an upper reinforcement member welded to the outer panel at a position above the impact bar, is disclosed. The reinforcement device further includes a plurality of first reinforcement members having a U-shaped strip configuration, and a second reinforcement member perpendicularly welded along the longitudinal center of the inner surface of each of the first members. In addition, the first members are vertically fitted into the lower portion of inner and outer panels at regularly spaced positions. An upper sub-reinforcement member extends from the top portion of each of the first member and welded to the upper reinforcement member.