A vehicular detector configured to transmit and receive a radio signal with a reader provided in a vehicle, detect seating of an occupant on a seat in the vehicle, and transmit a detection signal, the vehicular detector comprising: a first flexible sheet; a second flexible sheet placed opposite to the first flexible sheet; and an insulation sheet having electrical insulating property and intervening between the first flexible sheet and the second flexible sheet, characterized in that the first flexible sheet includes an antenna unit formed on a surface as a conductive pattern and configured to receive a transmission signal including a power supply radio signal from the reader, and a first contact portion electrically connected to the antenna unit and formed on a first opposing surface facing the second flexible sheet, the second flexible sheet includes a controller formed on a surface as a conductive pattern and configured to be driven by the transmission signal received by the antenna unit and output the detection signal, and a second contact portion electrically connected to the controller and formed on a second opposing surface facing the first flexible sheet, the insulation sheet has a through hole that, at a position where the first contact portion and the second contact portion face, runs through from the first opposing surface to the second opposing surface, and the first contact portion and the second contact portion become a state of making contact with each other by an external force based on seating of the occupant, cause the antenna unit to output the transmission signal to the controller, and cause the controller to output the detection signal to the antenna unit. a first flexible sheet; a second flexible sheet placed opposite to the first flexible sheet; and an insulation sheet having electrical insulating property and intervening between the first flexible sheet and the second flexible sheet, characterized in that the first flexible sheet includes an antenna unit formed on a surface as a conductive pattern and configured to receive a transmission signal including a power supply radio signal from the reader, and a first contact portion electrically connected to the antenna unit and formed on a first opposing surface facing the second flexible sheet, an antenna unit formed on a surface as a conductive pattern and configured to receive a transmission signal including a power supply radio signal from the reader, and a first contact portion electrically connected to the antenna unit and formed on a first opposing surface facing the second flexible sheet, the second flexible sheet includes a controller formed on a surface as a conductive pattern and configured to be driven by the transmission signal received by the antenna unit and output the detection signal, and a second contact portion electrically connected to the controller and formed on a second opposing surface facing the first flexible sheet, a controller formed on a surface as a conductive pattern and configured to be driven by the transmission signal received by the antenna unit and output the detection signal, and a second contact portion electrically connected to the controller and formed on a second opposing surface facing the first flexible sheet, the insulation sheet has a through hole that, at a position where the first contact portion and the second contact portion face, runs through from the first opposing surface to the second opposing surface, and the first contact portion and the second contact portion become a state of making contact with each other by an external force based on seating of the occupant, cause the antenna unit to output the transmission signal to the controller, and cause the controller to output the detection signal to the antenna unit.