Breaker, safety circuit and secondary battery pack

A breaker comprising:

• a first terminal piece on which a fixed contact is formed,
• a movable piece with a movable contact for pressing the movable contact against the fixed contact so as to contact therewith,
• a thermally-actuated element deforming with a change in temperature and moving the movable piece so that the movable contact is separated from the fixed contact, and
• a second terminal piece electrically connected to the movable piece,
• wherein
• the movable contact includes
• a first movable contact arranged at a first end portion of the movable piece in its longitudinal direction, and
• a second movable contact arranged at a second end portion of the movable piece in the longitudinal direction, and
• the fixed contact includes
• a first fixed contact arranged at a position with which the first movable contact can contact, and
• a second fixed contact arranged at a position with which the second movable contact can contact, wherein
• the movable piece has a first contact region contacting with the second terminal piece, between the first movable contact and the second movable contact.