To provide a process for producing a flexible polyurethane foam, which can suitably form a flexible polyurethane foam having a good cushioning characteristic by using a raw material derived from a natural fat/oil. The process comprises a step of reacting a polyoxyalkylene polyol (A) containing the first polyoxyalkylene polyol (A1) obtained by ring-opening polymerization of an alkylene oxide (c) with an initiator (b) in the presence of a polymerization catalyst (a), with a polyisocyanate compound (B) in the presence of a catalyst (C) and a blowing agent (D). The polymerization catalyst (a) is at least one member selected from the group consisting of a coordination anionic polymerization catalyst and a cationic polymerization catalyst, and the initiator (b) is a polyol derived from a natural fat/oil, which is obtained by providing a natural fat/oil with hydroxyl groups through a chemical reaction, and has a hydroxyl value of from 20 to 250 mgKOH/g and a ratio of the mass average molecular weight to the number average molecular weight calculated as polystyrene, (Mw/Mn), of at least 1.2.