Photodynamic Inactivation (PDI) research has been conducted as a method of photodynamic therapy that combines blue diode laser light (405 nm) with Alfalfa chlorophyll photosensitiser so that it can produce reactive oxygen species that cause biological damage to the target. This study aims to determine the potential of blue diode lasers and the addition of 20% chlorophyll photosensitiser to reduce gram-positive Staphylococcus aureus and gram-negative Pseudomonas aeruginosa which can cause skin infections. The method used is a blue diode laser irradiation of bacteria by the addition of chlorophyll and Total Plate Count (TPC) to determine the decrease in bacterial viability in units of CFU / ml. Test results show that photodynamic inactivation with a blue diode laser and chlorophyll can reduce bacterial viability. Irradiation for 180 seconds at a dose of 1.59 J / cm2 gives the most bacterial death results. The percentage of bacterial death of Staphylococcus aureus was (35.44 ± 1.67)% without photosensitiser, and with photosensitiser the percentage of bacterial deaths increased to (53.59 ± 1.36)%. While the percentage of Pseudomonas aeruginosa bacterial deaths was (20.02 ± 0.76)% without photosensitisers, and with additional photosensitisers it increased to (44.24 ± 1.50)%.