A transformer with a bobbin for preventing a crack may include a lower core configured to be provided with a lower assembling jaw, a bobbin for preventing a crack configured to have a center rib which is provided with a lower core crack preventing part inserted into the lower assembling jaw and an upper core crack preventing part formed at an opposite side to the lower core crack preventing part, having a predetermined thickness, a bus bar configured to penetrate through the center rib, an insulating plate configured to be stacked on an upper end surface of the bus bar, and an upper core inserted into the insulating plate and the bus bar and inserted into the upper core crack preventing part.