A treatment liquid that is a treatment liquid used in a manufacturing method for a cured substance, the manufacturing method including a film forming step of applying a resin composition containing a precursor of a cyclization resin onto a base material to form a film, a treatment step of bringing a treatment liquid into contact with the film, and a heating step of heating the film after the treatment step, the treatment liquid comprising:
- at least one compound selected from the group consisting of a basic compound having an amide group and a base generator having an amide group.