Tribolium castaneum is a major pest in wheat flour but can attack other processed foodstuffs. Control of these pests can be done in various ways, one of them by biological control using entomopathogenic fungus Beauveria bassiana. This study aims to determine the infectivity of B. bassiana entomopathogenic fungus against T. castaneum populations in the laboratory. The experiment was completed with random preparations, each preparation was repeated three times. Imago T. castaneum was sprayed with a conidia suspension of B. bassiana at a density of 106 and 107 conidia/mL on three different storage media namely PDA, rice, and corn media. Mortality was calculated based on the percentage of imago that died of B. bassiana fungi. One week observation showed the mortality of T. castaneum after the application of B. bassiana fungus was 55.33% with 107 conidia/mL in corn media. The highest spore density was found in rice media with an average of 10.53 x 106 conidia/mL. Meanwhile, the value of the results showed LC50 of 2.11 x 107 conidia/mL and the fastest LT50 in corn media was 5.31 days