The invention discloses an ultrathin minitype breaker, which comprises an outer shell, an operating mechanism, a contact mechanism, an overcurrent protection mechanism, a short circuit protection mechanism, an arc extinguishing mechanism and a fastener. The short circuit protection mechanism comprises a magnet yoke, a coil, a coil shell, a movable iron core, a static iron core, an iron core spring and a push rod. The magnet yoke is made of a composite copper steel material, a side corner formed by bending a long piece corner close to the lower end of an arcing shield is welded with one end of the coil by spot welding, and the other end of the coil is connected with a static connecting plate through a flexible lead. A plurality of single-pole ultrathin minitype breakers are integrated through a handle and a lock catch in the operating mechanism to form a multipole ultrathin minitype breaker. The ultrathin minitype breaker has the advantages of having the thickness of only 9mm which is half that of a traditional small breaker, breaking through the traditional design concept, saving cost due to the fact that a distribution box occupies less space due to an ultra-small size of the breaker, and having good performance.