PROBLEM TO BE SOLVED: To provide a living body detection system capable of correctly detecting whether a living body such as a care receiver is mounted on a living body signal sensor.SOLUTION: The living body detection system B includes: a living body signal sensor A in which a first electrode 12 is integrally laminated on one side of a piezoelectric sheet 11 and a second electrode 13 is integrally laminated on the other side of the piezoelectric sheet 11, and an electret sheet 19, a deformation layer 14 deformed by pressure in an elastically restorable manner and a third electrode 15 are integrally laminated on the second electrode 13 in this order a first measurement part 2 for measuring a potential between the second electrode and the third electrode a second measurement part 3 for measuring a potential generated by the piezoelectric sheet 11 and a control part 4 for determining the existence/absence of a living body on the basis of measurement results of the first measurement part 2 and the second measurement part 3 to output the existence/absence of the living body to an output part 5.
