A sitting sensor comprising: a pair of insulating sheets (10P, 20P); a spacer disposed between the pair of insulating sheets (10P, 20P) and having a plurality of openings (11H, 12H, 13H, 21H, 22H, 23H); a plurality of pressure-sensitive switches including a pair of electrodes (11F, 12F, 13F, 11S, 12S, 13S, 21F, 22F, 23F, 21S, 22S, 23S) facing each other at the plurality of openings; and a pair of terminals (T1, T2), wherein the plurality of pressure-sensitive switches is configured by at least two first pressure-sensitive switches (SW11, SW12, SW13) including one first specific pressure-sensitive switch and at least two second pressure-sensitive switches (SW21, SW22, SW23), and has a first pressure-sensitive switch group including the at least one first pressure-sensitive switch (SW11, SW12, SW13) including the one first specific pressure-sensitive switch and the at least one second pressure-sensitive switch (SW21, SW22, SW23), and the second pressure-sensitive switch group including the at least two first pressure-sensitive switch including the first specific pressure-sensitive switch and the at least one second pressure-sensitive switch that is different from the second pressure-sensitive switch of the first pressure-sensitive switch group, in the first pressure-sensitive switch group, the first specific pressure-sensitive switch is located at an end of the first pressure-sensitive switch group, and the first pressure-sensitive switch (SW11, SW12, SW13) and the second pressure-sensitive switch (SW21, SW22, SW23) are disposed adjacent to each other along a left-right direction of a seat, in the second pressure-sensitive switch group, the first specific pressure-sensitive switch is located at an end of the second pressure-sensitive switch group, and the first pressure-sensitive switch and the second pressure-sensitive switch are alternately disposed adjacent to each other along a front-rear direction of the seat, and the first pressure-sensitive switch and the second pressure-sensitive switch are connected in series, and turning on the at least one first pressure-sensitive switch and the at least one second pressure-sensitive switch causes a current to flow between the pair of terminals (T1, T2). a pair of insulating sheets (10P, 20P); a spacer disposed between the pair of insulating sheets (10P, 20P) and having a plurality of openings (11H, 12H, 13H, 21H, 22H, 23H); a plurality of pressure-sensitive switches including a pair of electrodes (11F, 12F, 13F, 11S, 12S, 13S, 21F, 22F, 23F, 21S, 22S, 23S) facing each other at the plurality of openings; and a pair of terminals (T1, T2), wherein the plurality of pressure-sensitive switches is configured by at least two first pressure-sensitive switches (SW11, SW12, SW13) including one first specific pressure-sensitive switch and at least two second pressure-sensitive switches (SW21, SW22, SW23), and has a first pressure-sensitive switch group including the at least one first pressure-sensitive switch (SW11, SW12, SW13) including the one first specific pressure-sensitive switch and the at least one second pressure-sensitive switch (SW21, SW22, SW23), and the second pressure-sensitive switch group including the at least two first pressure-sensitive switch including the first specific pressure-sensitive switch and the at least one second pressure-sensitive switch that is different from the second pressure-sensitive switch of the first pressure-sensitive switch group, in the first pressure-sensitive switch group, the first specific pressure-sensitive switch is located at an end of the first pressure-sensitive switch group, and the first pressure-sensitive switch (SW11, SW12, SW13) and the second pressure-sensitive switch (SW21, SW22, SW23) are disposed adjacent to each other along a left-right direction of a seat, in the second pressure-sensitive switch group, the first specific pressure-sensitive switch is located at an end of the second pressure-sensitive switch group, and the first pressure-sensitive switch and the second pressure-sensitive switch are alternately disposed adjacent to each other along a front-rear direction of the seat, and the first pressure-sensitive switch and the second pressure-sensitive switch are connected in series, and turning on the at least one first pressure-sensitive switch and the at least one second pressure-sensitive switch causes a current to flow between the pair of terminals (T1, T2).