Abstract: A hollow fiber membrane, wherein an inner diameter (Id) is within the range of 100 to 200 &mgr;m, the ratio (Mt/Id) of a wall thickness (Mt) to the inner diameter (Id) is the range of 0.9 to 1.1, a bubble point (Bp) is at least 0.5 MPa, and the ratio (Di/Do) of the maximum major axis (Di) of the pores existing in the layer of up to 10 &mgr;m thick from an inner surface to the maximum major axis (Do) of the pores existing in the layer of up to 10 &mgr;m thick from an outer surface is within the range of 10.0 to 15.0; a hollow fiber membrane module formed of the hollow fiber membranes; and a water purifier formed of the hollow fiber membrane module.