Poly(methyl methacrylate) (PMMA) is widely used for transferring chemical vapor deposition grown graphene. The residue of PMMA after the transfer degrades the electronic properties of the graphene, and the complete removal of PMMA has been a challenging issue. Annealing in Ar/H2 gas flow has been commonly adopted to remove the PMMA residue. We studied the effect of annealing on graphene in the wide temperature range of 350-800 °C using Ar/H2 forming gas, systematically. The conductivity was increased at moderate temperatures, but decreased at excessive temperatures higher than 650 °C. On the other hand, the PMMA residue was not removed effectively in all temperature ranges, judging from Raman spectroscopy and atomic force microscopy. By analyzing Raman spectroscopic data, chemisorption of PMMA residue on graphene was confirmed.