Disclosed are a treating liquid for photoresist removal, containing (a) an oxidizing agent (e.g., aqueous hydrogen peroxide), (b) at least one selected from alkylene carbonates and their derivatives (e.g., propylene carbonate), and (c) water; and a method for treating with the treating liquid a substrate having a photoresist film deteriorated after dry-etching treatment thereof or a substrate optionally subjected to plasma-ashing treatment after the dry-etching treatment, and then treating it with a photoresist-stripping liquid for stripping off the photoresist.