A signal detection device includes: multiple electrodes that are arranged to come into contact with a subject that generates a signal； an electrode signal selection unit that alternatively selects one signal from signals on the multiple electrodes based on a selection signal； an amplification unit that amplifies the signal that is selected by the electrode signal selection unit； and a flexible substrate on which the multiple electrodes, the selection unit, and the amplification unit are formed, in which the amplification unit is formed on the substrate to form a laminated structure together with the multiple electrodes and the selection unit.
