Data completeness of digital maps, referring to the degree of road data covering the reality, is one of essential data quality indexes. Examining the data completeness of two governmental digital maps in Taiwan had been conducted by sampling methods, which is not able to thoroughly ensure and improve a digital map’s data quality. This paper summarized a lesson learned from performing an examination task by the author for an official digital map of Ministry of Transportation and Communication, Taiwan in 2014. Using another official map data issued by the Ministry of Interior, Taiwan as the benchmark, a workflow of examination was proposed that can quantitatively determine the data completeness of a digital map by thoroughly contrasting the geometric data of the two digital maps. The workflow effectively reduced the cost of manual work; meanwhile, the data completeness can also be significantly improved by correcting the omission and commission data identified by the process.