It is not illegal to earn exchange rate difference in Africa, but the specific situation depends on the laws and regulations of different countries. In some African countries, the government may restrict or supervise foreign exchange transactions to ensure the stability of the domestic foreign exchange market. Some countries may formulate fixed exchange rate and foreign exchange control policies to keep the value of their currencies stable. Therefore, individuals or institutions that illegally profit from exchange rate differences in these countries may violate local laws.

In addition, illegally profiting from exchange rate differences may lead to capital flow problems and economic instability. Pursuing the profit of exchange rate difference may lead to the devaluation of domestic currency, affect exports and lead to the decline of economic competitiveness.

Therefore, if you are interested in profiting from the exchange rate difference in Africa, you should carefully understand and abide by local foreign exchange laws and regulations.