To provide a flexible polyurethane foam which is excellent in low resiliency and durability without using a plasticizer and which shows little change in hardness against a change in temperature and at the same time, has high air flow.A process for producing a flexible polyurethane foam, which comprises reacting a polyol mixture comprising the following polyol (A), the following polyol (B) and the following monool (D) with a polyisocyanate compound in the presence of a blowing agent and a foam stabilizer, at an isocyanate index of at least 90, wherein: Polyol (A) is a polyether polyol having an average of from 2 to 3 hydroxyl groups, a hydroxyl value of from 10 to 60 mgKOH/g and an oxyethylene group content of from 0 to 30 mass %, obtained by ring-opening polymerization of an alkylene oxide to an initiator using a phosphazene compound, a Lewis acid compound or an alkali metal compound catalyst; Polyol (B) is a polyether polyol having an average of from 2 to 3 hydroxyl groups and a hydroxyl value of from 70 to 250 mgKOH/g; and Monool (D) is a polyether monool having a hydroxyl value of from 10 to 200 mgKOH/g.