Amsterdam is not a city known for its beautiful Christmas Markets, so if you would like to visit a city with beautiful Christmas Markets you should probably visiting the Christmas Markets in Vienna or the Christmas Markets in Paris instead.
But, if you are still heading for Amsterdam and would like some kind of a Christmas Market we would recommend that you go to the Albert Cuypstraat where you can find a street with very nice atmosphere and cool Christmas stuff. There are also some other markets around Amsterdam, but these are mostly open for a day or two only, so if you bump into them, good for you.
Where is Albert Cuypstraat? It is not very far from Rijksmuseum and the Van Gogh Museum. Check the map further down for more instructions.