PURPOSE: To provide a bonding strength testing method for solder in which heating and pressurization can be controlled easily at the time of bonding a test piece while attaining a pure torque load state.

CONSTITUTION: A flat board 1 applied with paste solder 7 in ring shape is superposed by another flat board 2 and two flat boards 1, 2 are subjected to torque load while being heated and pressurized. Alternatively, one flat board 1 provided with a solder coating part between double ring grooves is applied with paste solder 7 and superposed by another flat board 2 having same structure and then two flat boards 1, 2 are subjected to torque load while being heated and pressurized.