Buying and selling foreign exchange outside the designated foreign exchange banks and China Foreign Exchange Trading Center and its sub-centers, the amount of which is more than 200,000 US dollars, or the illegal income is more than 50,000 yuan, shall be investigated by the public security organ on suspicion of illegal business operation in accordance with the provisions of Article 225 of the Criminal Law, and criminal responsibility shall be investigated; If the illegal trading of foreign exchange fails to meet the above prosecution standards, the foreign exchange administration department shall impose administrative penalties according to Article 45 of the Regulations on Foreign Exchange Administration; Those who refuse or obstruct state functionaries from performing their official duties of investigating and handling illegal foreign exchange activities according to law shall be dealt with by public security organs as appropriate.

It is not illegal for individuals to buy some for collection.

I have collected foreign currencies from dozens of countries.