PURPOSE: To reduce work processes and improve precision by installing a thin and long reinforcement member having a U-shaped cross section on a panel back surface by binding agent, and positioning and fixing both ends of it by pawls formed by press stamping and folding work to folded parts at panel upper and lower ends.

CONSTITUTION: A reinforcement member 2 having a U-shaped cross section is bound by binding agent to a back surface of a panel 1 formed by bending work. A female press die for lancing is engaged in the inner side of both end parts of the reinforcement member 2, so it is tightly applied to upper side parts 5 of the panel 1. Next, a male press die is pressurized from the outer side of the upper side parts 5, and the upper side parts 5 are stamped and folded simultaneously, so lanced pawls 10 are formed. The reinforcement member 2 is placed at a correct position by the pawls 10, and it is pressed to a back surface of the panel 1. As binding agent is hardened, the reinforcement member 2 is correctly and strongly installed.