To provide coupling structure of two members which is in little danger of the peripheral part of its screw hole being deformed and high in coupling strength.

Coupling structure is formed such that a screw 11 is inserted through a through-hole 8 formed in a side lever 5 being one member of two members about to be intercoupled, and by joining the screw 11 in a screwed-in state with a screw hole 4 formed in a vertical frame lever being the other plate-form member, the two members are intercoupled. The screw hole 4 of the vertical frame lever 2 is formed in the top part of an expansion part 17 expanded approximately in a conical shape in a direction in which the screw hole is separated away from the side lever 5.