A load detection device taking a film shape, comprising: a seat pad member and at least three detection sections (A to D) contacting a seating side surface of the vehicle seat pad member for detecting a load on the pad member; a connection section (24, 26, 28) connecting the detection sections (A to D); and a tail section connected to the connection section (24, 26, 28) within a sensing area surrounded by the at least three detection sections (A to D), bent downward within the sensing area, passing through a through hole (43, 73, 93, 103) that is provided to go through the pad member from the seating side surface to a back side within the sensing area to be wired to the back side of the pad member, and having at a lower end a lead portion for delivering load signals detected by the detection sections (A to D), wherein the tail section is connected at the lead portion to a harness provided with a socket; and the harness and the socket pass through the through hole (43, 73, 93, 103) that goes through a center portion of the seating surface of the vehicle seat pad member to the back side of the pad member; the harness is wired at the back side of the vehicle seat pad member; and the socket is connected to a vehicle side connector characterized in that a concave groove is formed to be depressed at a part on the seating side surface of the vehicle seat pad member transversely of the connection section, and the through hole is formed at a bottom portion of the concave groove; and a curved portion that is formed by curving at least a part of the connection section is inserted into the concave groove, and the tail section is bent to pass through the through hole. a seat pad member and at least three detection sections (A to D) contacting a seating side surface of the vehicle seat pad member for detecting a load on the pad member; a connection section (24, 26, 28) connecting the detection sections (A to D); and a tail section connected to the connection section (24, 26, 28) within a sensing area surrounded by the at least three detection sections (A to D), bent downward within the sensing area, passing through a through hole (43, 73, 93, 103) that is provided to go through the pad member from the seating side surface to a back side within the sensing area to be wired to the back side of the pad member, and having at a lower end a lead portion for delivering load signals detected by the detection sections (A to D), wherein the tail section is connected at the lead portion to a harness provided with a socket; and the harness and the socket pass through the through hole (43, 73, 93, 103) that goes through a center portion of the seating surface of the vehicle seat pad member to the back side of the pad member; the harness is wired at the back side of the vehicle seat pad member; and the socket is connected to a vehicle side connector characterized in that a concave groove is formed to be depressed at a part on the seating side surface of the vehicle seat pad member transversely of the connection section, and the through hole is formed at a bottom portion of the concave groove; and a curved portion that is formed by curving at least a part of the connection section is inserted into the concave groove, and the tail section is bent to pass through the through hole.