A sea-surface temperature lowering apparatus effectively lowers the temperature of seawater near a sea surface to allow low-temperature deep seawater pumped to around the sea surface to stay close to the sea surface without sinking immediately. The sea-surface temperature lowering apparatus includes a pump that pumps deep seawater. The pumped deep seawater and surface water are agitated to generate agitated water. The sea-surface temperature lowering apparatus includes a platform including the pump and an agitation device. The deep seawater with a low temperature and the surface water with a high temperature are mixed to generate the agitated water. This lowers the temperature of seawater near the sea surface without the deep seawater sinking immediately.