To uniformly flatten the heights of solder bumps deformed at contact time of a test and burn-in by constituting a vertically movable guide plate, having the same-shaped hole penetrated with plural divided pieces formed in the side tip part of the solder bumps of contact pins, to be horizontally supported by a guide plate column in an intermediate position by leaving the constant length on the tip.

Divided pieces of an arc-shaped projection are formed of, for example, two notches on the upper end of a springy plunger 3c in a cylinder 3a of plural contact pins 3 held by a pin support plate 4 in an IC socket. When the IC socket is moved upward, a guide plate 6 having a through-hole of the divided pieces is horizontally supported in an upper intermediate position, and the tip of the constant length projecting parts 7a of both side columns 7 erected on a support stand 5 abuts to the bottom surface of an IC 2, so that the contact pins 3 apply prescribed stresses to solder bumps 2a. When a test and burn-in are finished, the forefront of the downward deforming solder bumps 2a is regulated by the guide plate 6 to reduce the fluctuations in a height.