Background: Although inequality in traumatic brain injury (TBI) by individual socioeconomic status (SES) exists, interventions to modify individual SES are difficult. However, as interventions for area-based SES can affect the individual SES, monitoring or public health intervention can be planned. We analyzed the effect of area-based SES on hospitalization for TBI and revealed yearly inequality trends to provide a basis for health intervention. Methods: We included patients who were hospitalized due to intracranial injuries (ICIs) between 2008 and 2015 as a measure of severe TBI with data provided by the Korea National Hospital Discharge Survey. Area-based SES was synthesized using the 2010 census data. We assessed inequalities in ICI-related hospitalization rates using the relative index of inequality and the slope index of inequality for the periods 2008–2009, 2010–2011, 2012–2013, and 2014–2015. We analyzed the trends of these indices for the observation period by age and sex. Results: The overall relative indices of inequality for each 2-year period were 1.82 (95% confidence interval, 1.5–2.3), 1.97 (1.6–2.5), 2.01 (1.6–2.5), and 2.01 (1.6–2.5), respectively. The overall slope indices of inequality in each period were 38.74 (23.5–54.0), 36.75 (21.7–51.8), 35.65 (20.7–50.6), and 43.11 (27.6–58.6), respectively. The relative indices of inequality showed a linear trend for men (P = 0.006), which was most evident in the ≥ 65-year age group. Conclusion Inequality in hospitalization for ICIs by area-based SES tended to increase during the observation period. Practical preventive interventions and input in healthcare resources for populations with low area-based SES are likely needed.