We report the case of a 73-year-old woman with leukoderma induced by cosmetics containing ascorbic acid. She had noticed the sudden appearance of a hypopigmented macule on the cheek within 1 month after use of the cosmetics with the brand name Obaji C Serum. No history of use of rhododenol-containing cosmetics was declared. Histopathological analysis revealed that the number of matured melanocytes was apparently decreased, and T lymphocytes abundantly infiltrated mainly the perifollicular region. In addition to the discontinuation of using Obaji C Serum, phototherapy by excimer light was noticeably effective for repigmentation. To our knowledge, there has been no other report so far showing hypopigmented lesions induced by this cosmetic.