PURPOSE: To obtain a regenerated pulp causing little paper-breakage trouble in paper-making process and giving a paper having no black spot and few pinholes by dissociating waste heat-sensitive recording paper in an alkaline aqueous solution, adding and mixing a defoaming agent to the obtained pulp suspension and cleaning the mixture.

CONSTITUTION: Waste heat-sensitive recording paper is dissociated in an alkaline aqueous solution, a defoaming agent (e.g. a mixture of polyglycol and fatty acid) is added and mixed to the obtained pulp suspension and the mixture is cleaned to obtain regenerated pulp. When the waste paper has a protective layer, it is preferable to mechanically agitate the pulp suspension at a concentration of ≥15% under a compressive action prior to the cleaning treatment. When the waste paper contains color paper, the cleaned product is preferably bleached with an oxidation agent.