An apparatus for membrane distillation using a solar absorber (152,212), comprising: a raw water circulation pipe to circulate raw water in a raw water tank; a solar heat absorbing device (150,210) provided on one side of the raw water circulation pipe to heat the raw water in the raw water circulation pipe; a raw water tank to receive the raw water heated by the solar heat absorbing device (150,210) through the raw water circulation pipe and to supply the raw water to a membrane distillation module; the membrane distillation module to produce treated water from the raw water through a membrane distillation process; and a coolant tank to supply a coolant to the membrane distillation module and to collect the treated water produced by the membrane distillation module, wherein a phase change material (170,220) is provided on one side of the raw water tank, and the phase change material (170,220) is adapted to absorb heat of the raw water and is adapted to store the heat when a temperature of the raw water is equal to or higher than a melting point of the phase change material (170,220) of between 20°C and 60°C, and is adapted to release the stored heat when the temperature of the raw water is lower than the melting point of the phase change material (170,220), wherein an inner wall is provided at a location spaced from an inner surface of the raw water tank, and the phase change material (170,220) is provided in a space between the inner surface and the inner wall, the phase change material (170,220) provided between the inner surface and the inner wall surrounds the raw water of the raw water tank, and the space between the inner surface and the inner wall is spatially separated from a space in which the raw water of the raw water tank is provided. a raw water circulation pipe to circulate raw water in a raw water tank; a solar heat absorbing device (150,210) provided on one side of the raw water circulation pipe to heat the raw water in the raw water circulation pipe; a raw water tank to receive the raw water heated by the solar heat absorbing device (150,210) through the raw water circulation pipe and to supply the raw water to a membrane distillation module; the membrane distillation module to produce treated water from the raw water through a membrane distillation process; and a coolant tank to supply a coolant to the membrane distillation module and to collect the treated water produced by the membrane distillation module, wherein a phase change material (170,220) is provided on one side of the raw water tank, and the phase change material (170,220) is adapted to absorb heat of the raw water and is adapted to store the heat when a temperature of the raw water is equal to or higher than a melting point of the phase change material (170,220) of between 20°C and 60°C, and is adapted to release the stored heat when the temperature of the raw water is lower than the melting point of the phase change material (170,220), wherein an inner wall is provided at a location spaced from an inner surface of the raw water tank, and the phase change material (170,220) is provided in a space between the inner surface and the inner wall, the phase change material (170,220) provided between the inner surface and the inner wall surrounds the raw water of the raw water tank, and the space between the inner surface and the inner wall is spatially separated from a space in which the raw water of the raw water tank is provided.