Why Some countries Ban Microwave Oven ? ( I heard some countries 'Ban or  Going to Ban' Is it True ?)?

It toasts the brain.

Not that I've heard of. Which countries? Where have you heard this?

Not micro's but HEATING element appliances ARE not allowed into Cuba. They use a lot of electricity and Cuba is limited in available fuel for generating. MAYBE such restrictions are the reason for a supposed ban on m'waves. You can Google if of interest to you!

In the interest of Russia's credibility and accuracy of people's views of that country, I DID Google:

Japan is not banning microwave ovens. This rumor originated on a Russian satire website, was then picked up by several Spanish-language news outlets, and then went viral on Facebook. 

There you have it!

False rumors of Russia and Japan. Snopes says no to both. Nowhere that I could find have banned them.

which country's do you think are doing this? I think you will find its rubbish.