Background: This investigation comprised information from the Danish population to analyse the development of chronic non-cancer pain (CNCP) prevalence according to sex, age, physical job demand and educational level. Methods: Data derives from the Danish Health and Morbidity Surveys based on random samples of adults living in Denmark. The analysed samples were composed by 10,457 in 2000 (response rate: 62.7%), 5686 in 2005 (52.1%), 15,165 in 2010 (60.1%), 14,265 in 2013 (57.1%) and 14,022 in 2017 (56.1%). CNCP was defined as pain lasting 6 months or more. Individuals with a self-reported history of cancer were excluded. Calibration weighting was applied to reduce the impact of potential non-response bias. The Relative and the Absolute Concentration Index were calculated to measure educational inequalities. Results: CNCP prevalence has increased 8.3 percentage points during 2000–2017 (19.5%–27.8%) and is highest among women (22.1% to 30.8%). Higher CNCP prevalence among men aged 45–64 years exceeded the men aged >65 years in 2017 (31.9% and 29.8%, respectively). There was a continuous increase in CNCP prevalence in individuals with sedentary work or low physical demand at job from 2000 to 2017; among those with moderate or high physical demand at job the prevalence increased sharply from 2000 to 2010 after which the prevalence remained stable. Higher CNCP prevalence persisted among individuals with lower level of education regardless of gender and the inequalities remained stable over time. Conclusion: The Danish prevalence of chronic pain has increased in the last two decades and higher numbers are observed in some sociodemographic groups. Significance: This study provides an overview of the development of chronic non-cancer pain in a country and analyses the trends with socioeconomic inequalities. The continuous increasing prevalence may have huge social and economic implications. This study reveals an urgent need for measures to attenuate the increasing prevalence, which should be a priority for public health policy.