Can French citizens travel to Chinese mainland with a German visa?

Schengen Convention: People holding valid identity cards or visas of any member country can move freely within the territory of all member countries. According to the agreement, tourists can legally visit all other Schengen countries as long as they have a valid visa in one of them.

By 2003, the number of Schengen member countries had increased to 15: Austria, Belgium, Denmark, Finland, France, Germany, Iceland, Italy, Greece, Luxembourg, the Netherlands, Norway, Portugal, Spain and Sweden.

Just get one of the 15 countries.