A circuit breaker has a first and a second conducting strip respectively mounted in a lower end of a shell; a first terminal mounted on an upper end of the second conducting strip; a bimetal strip longitudinally mounted on an upper end of the first conducting strip; a second terminal detachably in contact with the first terminal; a button mounted on an upper end of the shell; and an arm pivotally mounted in an interior of the shell. An upper end of the bimetal strip is securely connected to a lower end of the arm. When the current is excessively high, the distortion of the bimetal strip in turn drives the arm and the button. The switch angle of the button is much bigger via the leg so that the switch angle of the button is obvious.