The shooting took place late yesterday when four armed men entered the salon and shot a 41-year-old through the skull and a 44-year-old through the abdomen, Madrid's ambulance service said.
Police said the four gunmen fled the scene in a car.
Emergency workers found one victim dead.
The wounded man was conscious and was taken to La Paz hospital, where he is in stable condition.
Emergency services also attended a woman - believed to be the dead man's partner - who was in shock and unable to speak when the ambulances arrived.