A signal detection device comprising: a first circuit layer having flexibility, in which multiple electrode groups, each of which is made from multiple electrodes (100 1 to 100 4) configured to come into contact with a subject that generates a signal, are arranged in the form of a matrix; a second circuit layer having flexibility, in which multiple amplification units, are arranged in the form of a matrix, and in which a second selection unit (GS 1 to GS n) is arranged, the selection unit being configured to select a detection signal which is output from each of the multiple amplification units that are arranged in the form of a matrix; and a conductive layer that is provided between the first circuit layer and the second layer; characterized in that: - the first circuit layer also comprises multiple first selection units, each of which is configured to select signals on the multiple electrodes (100 1 to 100 4) based on a selection signal, that are arranged in the form of a matrix; - each of the multiple amplification units is configured to amplify the signal selected by the first selection unit; - the conductive layer electrically connects an output part of the first selection unit that is formed on the first circuit layer and an input part of the amplification unit that is formed on the second circuit layer; - the first circuit layer and the second circuit layer are stacked with the conductive layer in between in such a manner that the amplification unit forms a laminated structure together with the electrode group that is made from the multiple electrodes and the first selection unit. a first circuit layer having flexibility, in which multiple electrode groups, each of which is made from multiple electrodes (100 1 to 100 4) configured to come into contact with a subject that generates a signal, are arranged in the form of a matrix; a second circuit layer having flexibility, in which multiple amplification units, are arranged in the form of a matrix, and in which a second selection unit (GS 1 to GS n) is arranged, the selection unit being configured to select a detection signal which is output from each of the multiple amplification units that are arranged in the form of a matrix; and a conductive layer that is provided between the first circuit layer and the second layer; characterized in that: - the first circuit layer also comprises multiple first selection units, each of which is configured to select signals on the multiple electrodes (100 1 to 100 4) based on a selection signal, that are arranged in the form of a matrix; - each of the multiple amplification units is configured to amplify the signal selected by the first selection unit; - the conductive layer electrically connects an output part of the first selection unit that is formed on the first circuit layer and an input part of the amplification unit that is formed on the second circuit layer; - the first circuit layer and the second circuit layer are stacked with the conductive layer in between in such a manner that the amplification unit forms a laminated structure together with the electrode group that is made from the multiple electrodes and the first selection unit. - the first circuit layer also comprises multiple first selection units, each of which is configured to select signals on the multiple electrodes (100 1 to 100 4) based on a selection signal, that are arranged in the form of a matrix; - each of the multiple amplification units is configured to amplify the signal selected by the first selection unit; - the conductive layer electrically connects an output part of the first selection unit that is formed on the first circuit layer and an input part of the amplification unit that is formed on the second circuit layer; - the first circuit layer and the second circuit layer are stacked with the conductive layer in between in such a manner that the amplification unit forms a laminated structure together with the electrode group that is made from the multiple electrodes and the first selection unit.