To obtain a new polyimide having more superior permeability, high separating selectivity, excellent chemical resistance, moisture resistance, etc., by constituting the polyimide out of a tetravalent residue derived from a tetracarboxylic acid dianhydride, and a divalent residue derived from a specific diamine component.

This polyimide has a repeating structural unit of formula I (R is a tetravalent group). The polyimide is obtained by carrying out the condensation polymerizatino of a tetracarboxylic acid diahydride of formula II (preferably pyromellitic dianhydride, etc.), with 2-(2,4-diaminobenzyl)pyridine of formula III. The objective polyimide has 303°C glass transition temperature and preferably has solubility in a polar solvent. The condensation polymerization is carried out by reacting the diamine component with the tetracarboxylic acid dianhydride in a polar solvent such as dimethylsulfoxide at 0-20°C, and adding a dehydrating and cyclizing agent to the product to convert a polyamide-acid into the polyimide at 20-30°C.