PURPOSE: To provide a terminal structure for circuit breaker in which the extension of the butt part of a box type terminal metal fitting by the fastening of a screw can be surely prevented at low cost with a simple structure.

CONSTITUTION: A box type terminal metal fitting 3 is put on the base 2 of a circuit breaker 1. The box type terminal metal fitting 3 is formed into substantially a square section by bending a metal plate material, butting both end parts 3a, 3a to each other, and arranging the butt part on about the center part of a bottom plate part. The opening parts not surrounded by the metal plate of the box type terminal metal fitting 3 form a first insert hole 3A for inserting a cable and a second insert hole 3B for inserting a terminal seat 5, a screw insert hole 3C is provided on the top plate part, and a screw 4 is screwed to the screw insert hole 3C. At least a part of the terminal seat 5 inserted to the second insert hole 3B of the box type terminal metal fitting 3 is curved to form a space between the about the center part 5A of the terminal seat 5 and about the center part 3D of the bottom plate part of the box type terminal metal fitting 3.