Unilateral linear capillaritis (ULC) is a rare variant of pigmented purpuric dermatosis (PPD), also known as unilateral pigmented purpuric eruption or quadrantic capillaropathy. It is characterized clinically by asymmetrically distributed linear or segmental purpuric macules on the lower extremities, and usually fades spontaneously. A 10-year old girl presented with linearly distributed unilateral asymptomatic pigmented purpuric macules on the left lower extremity for 2 years. The patient had no history of the previous skin diseases and had not taken any medications. Skin biopsy revealed histopathological features of PPDs, such as perivascular infiltration of lymphocytes and extravasation of red blood cells. However, dense, band-like, dermal, inflammatory infiltrate was not found which differentiates the case from lichen aureus. We made diagnosis of ULC based on the clinical characteristics and histopathologic findings. Our patient did not receive any specific treatment and the lesions improved after 6 months. To our knowledge, ULC is an extremely rare disease and only around 10 cases have been reported world widely. Moreover, the case of ULC has not previously been reported in the Korean dermatology literature. So, we herein report a case of ULC which shows the characteristic unilateral segmental distribution on lower extremity.