Narrowband ultraviolet B (NB-UVB) induces different immunological features from broadband ultraviolet B and is effective for the treatment of various cutaneous diseases. UV exposure alters the morphology and function of epidermal Langerhans cells (LCs), which can elicit cutaneous immunosuppressive responses. Recent studies have proposed that LCs serve as immunoregulatory cells in UV-induced immune suppression. This study investigated the cellular mechanisms of NB-UVB-induced immune suppression, including its effects on LC migration. NB-UVB irradiation induced the migration of epidermal LCs from the skin to the draining lymph nodes in a time- and dose-dependent manner. Experiments in Lang-DTR knock-in mice confirmed that epidermal LCs rather than Langerin+ dermal dendritic cells are essential for NB-UVB-induced immune suppression. These findings indicate that LCs play a critical immunoregulatory role in NB-UVB-induced immune suppression and NB-UVB phototherapy.