Photosensitive psoriasis (PP) is a clinically well-known, but rare and poorly defined, psoriasis subset. A beneficial reaction to sunlight and artificial ultraviolet (UV) radiation is a common feature in most cases of psoriasis. However, it can lead to an exacerbation of psoriatic skin disease or new psoriatic lesions in some patients. We report here a patient with PP in whom the aggravation of psoriatic lesion could be induced by sun exposure and UV irradiation. The patient, 34-year-old woman was diagnosed with psoriasis vulgaris 18 years ago. She has no heredity of photosensitivity and history of medication possibly inducing photosensitivity. After sun exposure or therapeutic narrow band UVB, she occasionally has experienced an exacerbation of lesions, especially the lesion on the arm and leg. The symptom remarkably develops in the spring or early summer. She has visited our clinic periodically and the lesions have been controlled with topical agents, steroid and vitamin D3 analogue. Patients with PP have a statically significant higher frequency of skin type 1, heredity of photosensitivity, advanced age, difficulties in therapy, and face and hands involvement compared with non-photosensitive patients. We report the impressive case of photosensitive psoriasis.