Submitted on 3 Jan 2008 (v1), last revised 19 Jun 2008 (this version, v2).-- 7 pages, 4 figures; references added, published version in Phys. Rev. D.-- PACS numbers: 95.35.+d, 98.80.Cq.We consider cosmological consequences of a heavy axino, decaying to the neutralino in R-parity conserving models. The importance and influence of the axino decay on the resultant abundance of neutralino dark matter depends on the lifetime and the energy density of axino. For a high reheating temperature after inflation, copiously produced axinos dominate the energy density of the universe and its decay produces a large amount of entropy. As a bonus, we obtain that the upper bound on the reheating temperature after inflation via gravitino decay can be moderated, because the entropy production by the axino decay more or less dilutes the gravitinos.K.-Y.C. is supported by the Ministerio de Educación y Ciencia of Spain under Proyecto Nacional FPA2006-05423 and by the Comunidad de Madrid under Proyecto HEPHACOS, Ayudas de I+D S-0505/ESP-0346, J.E.K. is supported in part by the KRF Grants, No. R14-2003-012-01001-0 and No. KRF-2005-084-C00001, H.M.L. is supported by DOE Contracts DOE-ER-40682-143 and DEAC02-6CH03000, and O.S. is supported by the MEC project (No.FPA 2004-02015) and the Comunidad de Madrid project HEPHACOS (No. P-ESP-00346). K.-Y.C. and O.S. would like to thank the European Network of Theoretical Astroparticle Physics ILIAS/ENTApP under contract number RII3-CT-2004-506222 for financial support.Peer reviewed