A liquid treatment device (100) including: a structure (10) having a first surface (10a) and a second surface (10b), the structure including: a conductor (11) arranged between the first surface (10a) and the second surface (10b), the conductor including a first portion (11a) exposed to outside at the first surface (10a) and a second portion (11b) exposed to outside at the second surface (10b), and the conductor electrically connecting the first portion (11a) and the second portion (11b); and an ion transfer layer (15) arranged between the first surface (10a) and the second surface (10b), the ion transfer layer (15) arranged between the first surface (10a) and the second surface (10b), allowing hydrogen ions to move therethrough; and a first treatment tank (12) for holding a first liquid to be treated (17) therein, wherein the first surface (10a) of the structure (10) is located inside the first treatment tank (12).