A method for manufacturing a thin film solar cell includes: depositing a transparent first rear electrode on a first surface of a transparent substrate; depositing a second rear electrode having a high-conductive metal on the first rear electrode; performing a first laser scribing process to separate a double layer of the first and second rear electrodes; depositing a light absorption layer having selenium (Se) or sulfur (S) on the second rear electrode; performing a second laser scribing process by inputting a laser to a second surface of the transparent substrate to separate the light absorption layer; depositing a transparent electrode on the light absorption layer; and performing a third laser scribing process by inputting a laser to the second surface to separate the transparent electrode. Accordingly, patterning may be performed in a substrate-incident laser manner to improve price, productivity and precision of the patterning process.