Polyether polyol production method and polyurethane foam production method

A method of producing a polyether polyol (F), comprising:

• step (1) of obtaining a crude polyether polyol composition (D2) having a pH higher than 5.0 by contact of a crude polyether polyol composition (D1) containing a polyether polyol (A) with an acid catalyst (B) in the presence of water, the polyether polyol (A) being obtainable by ring-opening polymerization of an alkylene oxide with an active hydrogen compound;
• and
• step (2) of removing a volatile component containing an aldehyde (C) after step (1),
• wherein the acid catalyst (B) is either a solid acid catalyst (B1) or a Lewis acid catalyst (B2),
• wherein the solid acid catalyst (B1) has a solubility of 0.1 g or less in 100 g of the polyether polyol (A) at 80° C., and
• wherein the Lewis acid catalyst (B2) has a solubility of more than 0.1 g in 100 g of the polyether polyol (A) at 80° C.