A biological signal measuring system includes a sensor and a biological signal measuring apparatus configured to calculate a blood refill time of a living tissue of a subject. The sensor includes a pressure applying portion configured to apply pressure on the living tissue, a light emitter confgured to emit light toward the living tissue, a light receiver configured to receive reflected light or transmitted light from the living tissue, a first light transmitting member made of a light transmitting material and having one side contacting the light emitter and the other side arranged to contact the subject, a second light transmitting member made of a light transmitting material and having one side contacting the light receiver and the other side arranged to contact the subject, and a light blocking member configured to block light between the light emitter and the light receiver.
