An instant trip device of a circuit breaker, the instant trip device comprises: a magnet configured to generate a magnetic absorbing force with power applied thereto; a support disposed at a side opposite to the magnet; an armature which is provided between the magnet and the support, and which includes a rotation center portion, and wherein a rotating part is disposed to be rotatable with respect to the rotation center portion; an armature spring configured to apply an elastic force in a direction where the rotating part of the armature becomes farther away from the magnet; a groove of which one side is opened, the groove being formed at the support to support the rotation center portion of the armature; and a boss formed at the rotation center portion of the armature, wherein the boss is arranged to be inserted into the groove, wherein the armature spring is an extension spring in which one end of the armature spring is supported by a first hanger included in the support, and the other end of the armature spring is supported by a second hanger included in the rotating part of the armature, wherein the opened one side of the groove is formed in a direction of the rotating part, characterized in that the support comprises a spring accommodating part which is formed at a side of the first hanger for the armature spring to pass through the support, so that there is no interference between the support and the armature spring, the armature includes a first moving plate that is the rotating part and a second moving plate that is bent to be perpendicular to the first moving plate, wherein the rotation center portion is formed in the second moving plate, the support, the armature, and the armature spring are assembled as an assembly, which is separate from the magnet, and in that the support further comprises a first fixed plate having the spring accommodating part, and the first fixed plate is configured to limit a rotation of the rotating part in the direction where the rotating part of the armature becomes farther away from the magnet. a magnet configured to generate a magnetic absorbing force with power applied thereto; a support disposed at a side opposite to the magnet; an armature which is provided between the magnet and the support, and which includes a rotation center portion, and wherein a rotating part is disposed to be rotatable with respect to the rotation center portion; an armature spring configured to apply an elastic force in a direction where the rotating part of the armature becomes farther away from the magnet; a groove of which one side is opened, the groove being formed at the support to support the rotation center portion of the armature; and a boss formed at the rotation center portion of the armature, wherein the boss is arranged to be inserted into the groove, wherein the armature spring is an extension spring in which one end of the armature spring is supported by a first hanger included in the support, and the other end of the armature spring is supported by a second hanger included in the rotating part of the armature, wherein the opened one side of the groove is formed in a direction of the rotating part, characterized in that the support comprises a spring accommodating part which is formed at a side of the first hanger for the armature spring to pass through the support, so that there is no interference between the support and the armature spring, the armature includes a first moving plate that is the rotating part and a second moving plate that is bent to be perpendicular to the first moving plate, wherein the rotation center portion is formed in the second moving plate, the support, the armature, and the armature spring are assembled as an assembly, which is separate from the magnet, and in that the support further comprises a first fixed plate having the spring accommodating part, and the first fixed plate is configured to limit a rotation of the rotating part in the direction where the rotating part of the armature becomes farther away from the magnet.