BERLIN—German Chancellor Angela Merkel is stepping up her efforts to stem migration to Europe at the source, flying to Africa this weekend and working to convince Germans that better conditions in developing countries are in their own interests.

In a three-day swing through Mali, Niger, and Ethiopia starting Sunday, Ms. Merkel will discuss German development aid and ways to prevent young Africans from attempting the perilous land-and-sea journey to Europe. After she returns, she will meet the presidents of Chad and Nigeria...