A liquid actuator, which contains: an electrolyte layer (14, 114) containing a liquid, two or more electrically separated electrode parts (13a, 13b, 113a, 113b) on one or both sides of the electrolyte layer, and a water-repellent layer (12, 112) having a porous structure on an outside surface of at least one of the electrode parts, in which the electrolyte layer (14, 114), the electrode parts (13a, 13b, 113a, 113b), and the water-repellent layer (12, 112) form a structural body, wherein voltage is applied across the plural electrode parts (13a, 113a) including the one provided with the water-repellent layer (12, 112), and the applied voltage is adjusted to change the superficial wettability of the structural body.