Cancer was ranked as the second leading cause of global mortality in 2019, with an increasing incidence. An adequate workforce of healthcare professionals with special skills and knowledge in cancer care is vital for addressing the disparities in cancer prognosis. This study aimed to elucidate the trends in the advanced practice nursing workforce (APNW) in cancer care, which included certified nurse specialists (CNSs) and certified nurses (CNs) in each prefecture of Japan from the system's inception to the present. Further, it sought to analyze the regional disparities and compare these trends with other healthcare resources to identify contributing factors associated with the APNW in cancer care in each prefecture. We performed a panel data analysis using publicly available data on the APNW in cancer care in each prefecture of Japan from 1996 to 2022. Gini coefficients were calculated to examine the trends in geographic equality. Univariate and multivariable fixed effect panel data regression models were used to examine regional factors associated with an APNW in cancer care. From 1996 to 2012, the APNW in cancer care increased from four to 6982 staff, while their Gini coefficients decreased from 0.79 to 0.43. However, from 2012 to 2022, the Gini coefficients decreased slightly from 0.43 to 0.41. The coefficient value was comparable to that for the disparity between hospital doctors (0.43) but more pronounced compared to those for other medical resources, such as hospitals (0.34), hospital nurses (0.37), and designated cancer care hospitals (0.29). The APNW in cancer care in each prefecture was significantly associated with a higher number of designed cancer care hospitals in the previous year (see first quartile, the coefficient for second quartile: 0.31, 95% confidence interval (CI) 0.21-0.40), and a fewer number of hospital doctors (-1.89, 95%CI -2.70 to -1.09). The size of the APNW in cancer care has increased since the system was established in 1996 up till 2022. With the increase in numbers, geographic inequality narrowed until 2012 and has since then remained stagnant.