Abstract: An ultra-compact phototherapy apparatus for treating skin diseases includes: a PCB substrate in which a light emitting element and a pair of left and right first metal electrodes (positive pole) are formed on an upper surface and a second metal electrode is formed on a lower surface, a battery having a first electrode on an upper surface, which is in contact with the second metal electrode on the lower surface of the PCB substrate, and a second electrode on a lower surface, and an electrode body formed so that the battery is inserted inside and the PCB substrate is inserted in slidingly a front-rear direction, of which an upper inner side is selectively in contact with the first metal electrode of the PCB substrate.