Composite semipermeable membrane and method for producing composite semipermeable membrane

A composite semipermeable membrane, comprising:

• a porous supporting membrane including a substrate and a porous support layer;
• and
• a separation functional layer disposed on the porous support layer,
• wherein
• the separation functional layer has an average pore radius measured by the positron annihilation lifetime measurement of 0.35 nm or more and 0.37 nm or less, the pore radius has a standard deviation of 0.023 nm or less, and
• a pure water permeability coefficient A and an average pore radius R (nm), which is measured by the positron annihilation lifetime measurement, satisfy a relationship such that A/R4 is 3.12×10−9 m/s/Pa/nm4 to 3.39×10−9 m/s/Pa/nm4.