A salt water desalination equipment comprising: a salt water supply unit operable to supply salt water to a reverse osmosis membrane component; a forward osmosis membrane component to which concentrated salt water discharged from the reverse osmosis membrane component is supplied; the forward osmosis membrane component has a concentrated salt water path to which the concentrated salt water is supplied and through which the concentrated salt water passes and a treated freshwater path to which treated freshwater is supplied and through which the treated freshwater passes, water molecules moves from the treated freshwater path to the concentrated salt water path by a forward osmotic phenomenon, and the forward osmosis membrane component produces mixed water to output a part of the mixed water to an assisting device and an assisting device to which a part of the mixed water discharged from the forward osmosis membrane component is supplied and which is connected to the salt water supply unit, wherein the assisting device increases the rotation capacity to the salt water supply unit, wherein the salt water supply unit is a salt water supply pump (201, 202) which is configured to rotate along a rotating shaft to supply salt water, the assisting device has a rotation assisting component which is directly connected to the rotating shaft configured to increase at least one of a rotating speed and a torque of the salt water supply pump, the rotation assisting component being configured to generate rotating force by a pressure of the supplied mixed water to increase at least one of the rotating speed and the torque of the salt water supply pump through the directly connected rotating shaft, wherein a pressure exchange unit is further disposed on an upstream side of the forward osmosis membrane component, the pressure exchange unit being configured to increase a pressure of the supplied concentrated salt water by using a part of the mixed water discharged from the forward osmosis membrane component. a salt water supply unit operable to supply salt water to a reverse osmosis membrane component; a forward osmosis membrane component to which concentrated salt water discharged from the reverse osmosis membrane component is supplied; the forward osmosis membrane component has a concentrated salt water path to which the concentrated salt water is supplied and through which the concentrated salt water passes and a treated freshwater path to which treated freshwater is supplied and through which the treated freshwater passes, water molecules moves from the treated freshwater path to the concentrated salt water path by a forward osmotic phenomenon, and the forward osmosis membrane component produces mixed water to output a part of the mixed water to an assisting device and an assisting device to which a part of the mixed water discharged from the forward osmosis membrane component is supplied and which is connected to the salt water supply unit, wherein the assisting device increases the rotation capacity to the salt water supply unit, wherein the salt water supply unit is a salt water supply pump (201, 202) which is configured to rotate along a rotating shaft to supply salt water, the assisting device has a rotation assisting component which is directly connected to the rotating shaft configured to increase at least one of a rotating speed and a torque of the salt water supply pump, the rotation assisting component being configured to generate rotating force by a pressure of the supplied mixed water to increase at least one of the rotating speed and the torque of the salt water supply pump through the directly connected rotating shaft, wherein a pressure exchange unit is further disposed on an upstream side of the forward osmosis membrane component, the pressure exchange unit being configured to increase a pressure of the supplied concentrated salt water by using a part of the mixed water discharged from the forward osmosis membrane component.