We report the annealing-temperature-dependent evolution of nanosized pits on a poly(methyl methacrylate) film spin-coated on a glass substrate. The pits are formed on the polymer surface as the toluene solvent evaporates rapidly. The depth and width of the pits are measured by atomic force microscopy after the film is annealed at ambient temperature, below and above the glass transition temperature (105 °C) of the polymer, respectively. Compared with the statistical results obtained at ambient temperature, the pits are shallow and narrow on the film annealed at 75 °C as molecular vibration expands the film. However, it is found that the pits are deeper and wider on the film annealed at 120 °C than on the films annealed at the other two temperatures, which results from the evaporation of the inner residual toluene in the polymer film.