A hollow fiber type semipermeable membrane which achieves both water permeability and selectivity in high level and performs efficient treatment using small membrane area utilizing the concentration difference from high concentration liquid having high osmotic pressure. The hollow fiber type semipermeable membrane is characterized in that, when an aqueous solution of 25° C. having NaCl concentration of 35 g/L and pressure of 1.0 MPa is flown into an outer side of the hollow fiber type semipermeable membrane having length of about 70 cm while freshwater of 25° C. having NaCl concentration of 0 g/L is flown into an inner side of one open end of the hollow fiber type semipermeable membrane and discharged from another open end at 10 kPa or less, the permeation flow rate is 30 to 70 L/m2/day. An inner diameter thereof is 50 to 200 μm; and the hollow ratio thereof is 24 to 42%.