A modularized transformer includes an annular iron core, a first module encircling the annular iron core, a second module encircling the first module, a third module encircling the second module, a fourth module encircling the third module, and a primary-side power supply line mounted on the fourth module and encircling the annular iron core. Thus, the modularized transformer has a modularized structure and includes multiple modules that are extended and increased to amplify the voltage or current continuously and to regulate the voltage or current.