A pulse oximeter is used widely on account of its convenience and very few complications. We experienced a case of accidental burning by a pulse oximeter sensor. An 83-year-old woman underwent total hip replacement surgery. A pulse oximeter (Oxisensor II N-25, Nellcor Puritan Bennett Inc., USA) was placed on the left index finger. The patient complained of pain on her index finger 5 minutes after the operation began. A localized skin burn was found underneath the sensor of the pulse oximeter. The skin burn healed without any sequelae.