<p>A deinking agent which comprises a compound having a C7-23 aliphatic hydrocarbon group, an oxyethylene group, and an oxypropylene group and/or oxybutylene group and having a degree of biodegradation of 60% or higher and an average molecular weight of 1,500 or lower. This deinking agent has satisfactory biodegradability and is reduced in the burden to be imposed on the environment. It provides satisfactory handleability because a moderate froth amount is maintained during the treatment. With the deinking agent, a high-quality regenerated pulp having a high whiteness and a low residual ink content can be obtained.</p>
