It's almost 40% atheist. What nation beats it? I'm only counting nations with freedom of religion though, not communist ones that ban religion.
Countries with freedom of religion whose population is over 40% atheist :
The Netherlands, Estonia, Cuba, Taiwan, Slovenia(not sure about this one), and a few others.
Countries where church attendance is lower than the Czech Republic:
Korea, South
Taiwan
Ukraine
Moldova
Bulgaria
Georgia
China
Armenia
Serbia and Montenegro
Belarus
Azerbaijan
Latvia
Norway
Denmark
Finland
Estonia
Iceland