Assalamu alaikum Is it haram to use microwave oven ? As food cooked in microwave oven can damage health.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

It is not permissible to use anything that is absolutely confirmed to be harmful to the person, as the Prophet said: "One should not harm himself or cause any harm to others." [Ahmad] Nonetheless, we do not know that using the microwave is harmful and that the food heated in it is harmful to one's health.

Ruling that something is forbidden because of its harm depends on the confirmation of such a harm. Islamic rulings are not based on doubt or rumours. Therefore, it is permissible to use the microwave which you inquired about in heating or cooking food unless the harm is confirmed, as in principle this is something permissible.

Allaah Knows best.